Keep WhatsApp & iMessage While Using a Data eSIM Abroad

30 Oct 2025

Travelling with a local data eSIM is the cheapest way to stay online. The worry: losing your WhatsApp or iMessage identity, missing OTPs, or triggering costly SMS activations. The good news is you can keep your home phone number on WhatsApp and iMessage while using a travel eSIM purely for data. The trick is line assignment: leave your home line for calls/SMS, set the eSIM as your data line, and avoid unnecessary reactivation prompts.

This guide shows you exactly how to do it on iPhone and Android, with step-by-step settings, what to tap when apps say “SIM changed”, and how to prepare backup codes so you’re never locked out. You’ll also find dual‑SIM examples for common trips and a quick troubleshooting section. If you’re heading to the US, Europe or beyond, pick an eSIM from Destinations and follow this playbook to keep your number, cut roaming costs, and stay reachable.

The simple rule: keep your number, switch your data

Keep your home SIM/eSIM active for calls and SMS (don’t remove it unless you’re certain you won’t need OTPs or calls).
Add a travel eSIM and assign it as the “Mobile Data”/“Preferred data” line.
Turn off data roaming on your home line to prevent surprise charges.
WhatsApp and iMessage will continue to use your home number over the travel eSIM’s internet connection.

Why this works: - WhatsApp is tied to the number you registered with, not the SIM providing data. As long as the app stays logged in and your device has internet, your WhatsApp identity stays the same. - iMessage and FaceTime can send/receive via your phone number and/or Apple ID email. Once activated on your number, iMessage continues to work over any internet connection.

Pre‑trip checklist (10 minutes now, hours saved later)

Confirm your phone is unlocked and supports eSIM/dual‑SIM.
Install critical updates for iOS/Android, WhatsApp, and Messages before you go.
Activate iMessage/FaceTime on your home number while still at home. Do not toggle iMessage off/on while abroad (it can trigger a paid international SMS).
WhatsApp:
Confirm you’re registered on your home number.
Enable two‑step verification and set your 6‑digit PIN with a recovery email.
Trigger a fresh chat backup (iCloud on iPhone, Google Drive on Android).
Two‑factor authentication:
Add an extra trusted number to your Apple ID, and note how to “Get Verification Code” from Settings offline.
For Android/Google services, generate and print/save your Google backup codes offline.
Add recovery methods for banks and key apps that send OTPs.
Decide your eSIM plan: single‑country or regional.
US trip: see Esim United States.
Western Europe: see Esim Western Europe or country packs like Esim France, Esim Italy, Esim Spain.
Multi‑country across US/Canada/Mexico: Esim North America.
Save your eSIM QR/activation details offline (PDF/screenshot in a secure note).
Label your lines clearly in your phone (Home vs Travel) to avoid slip‑ups.

Pro tip: Keep mobile data off on your home line. SMS usually works without data; you’ll still receive OTPs if your home number has roaming enabled for SMS. Check costs with your operator.

Set up on iPhone (dual‑SIM/eSIM)

1) Install and label your eSIM

Settings > Mobile Service (or Cellular) > Add eSIM.
Scan your eSIM QR or use the provider app.
When asked to label, name them clearly: - Primary or Home = your home number - Travel = your eSIM data plan

2) Assign lines for data, calls and SMS

Settings > Mobile Service: - Default Voice Line: Primary/Home (so your calls show your home number). - iMessage & FaceTime Line: Choose Primary/Home.
Mobile Data: - Set Mobile Data = Travel (eSIM). - Turn off Allow Mobile Data Switching (keeps data strictly on the eSIM).
For the Primary/Home line: - Turn off Data Roaming. - Leave the line enabled so SMS and calls can reach you.

Pro tip: For contacts who must always use your home number, set their per‑contact “Preferred Line” to Primary in the Contacts app.

3) iMessage and FaceTime settings that stick

Settings > Messages: - iMessage: ON (already activated on your home number before travel). - Send & Receive: Tick your phone number and Apple ID email. Set “Start New Conversations From” to your phone number if you want continuity, or your Apple ID email if your number can’t activate while abroad.
Settings > FaceTime: - Tick your phone number and Apple ID. Ensure your home number is active here too.

Avoid toggling iMessage or FaceTime OFF/ON while abroad. It can trigger a fresh activation SMS charged at international rates by your carrier.

4) WhatsApp: keep the same number

Open WhatsApp > Settings > Account > Two‑step verification: ensure it’s ON.
Do not use “Change Number” unless you are permanently changing numbers.
If WhatsApp shows “Did you change your number?” after it detects a SIM change, tap “No”.
If asked to re‑verify, only proceed if you can receive the SMS/voice call to your home number. Otherwise, force‑quit and reopen when you have signal for your home line or Wi‑Fi Calling.

Pro tip: Link WhatsApp Web/Companion on your laptop or tablet before you fly so you can keep chatting even if your phone is briefly offline.

Set up on Android (dual‑SIM/eSIM)

Android menus vary by brand, but the flow is similar.

1) Install and label your eSIM

Settings > Network & Internet > SIMs (or Connections > SIM Manager) > Add eSIM.
Label clearly: SIM 1 = Home, eSIM/SIM 2 = Travel.

2) Assign data, calls and SMS

Preferred SIM for:
Mobile data: Travel.
Calls: Home.
SMS: Home.
Turn off Data Roaming on the Home SIM.
Keep the Home SIM enabled so you can receive SMS/OTP.

Pro tip: Some Android phones let you choose SIM per contact in the dialler/Contacts. Set important contacts to always use your Home line.

3) Messages, RCS and Google account sanity checks

Google Messages (RCS chat features) may try to verify your number via SMS when re‑enabled. If prompted abroad, choose “Not now” to avoid a charge, or connect to Wi‑Fi with the Home SIM able to send one activation SMS.
Generate and save Google backup codes before you go, and add a recovery email/phone.

4) WhatsApp: same number, new data

Confirm WhatsApp is registered to your Home number.
Keep two‑step verification ON with your 6‑digit PIN.
If you see a SIM‑change prompt, choose “No” unless you’re truly changing numbers.
Re‑verification requires SMS/voice to your Home number; do this only when you have coverage and are comfortable with any roaming SMS cost.

Common prompts and how to respond

WhatsApp “Change number?” detected:
Choose “No”. You’re only using a different data connection, not changing identity.
iMessage wants to reactivate:
Don’t toggle iMessage/FaceTime while abroad.
If it deactivates unexpectedly, you can temporarily use your Apple ID email for send/receive, or reactivate knowing one international SMS may be charged by your carrier.
Google Messages RCS activation:
Select “Not now” and activate later on Wi‑Fi, or accept that one SMS may be sent.
SIM change notifications:
These are informational. As long as you don’t re‑register WhatsApp with a new number, your account stays tied to your Home number.

Pro tip: If you absolutely must remove your Home SIM, ensure every critical account has alternative 2FA (backup codes, authenticator app, recovery contacts) and that iMessage is set to send/receive via your Apple ID email.

Troubleshooting quick fixes

iMessage shows email instead of number:
Settings > Messages > Send & Receive: select your phone number. If it won’t tick, your Home line may lack coverage for activation. Use your Apple ID email temporarily and try activation later when the Home line has signal.
Not receiving WhatsApp codes:
Ensure the Home line is enabled and can receive SMS. Try voice call verification. If you can’t get the code, use WhatsApp Web on a linked device to stay connected until you can re‑verify.
Calls/SMS going out on the wrong line:
iPhone: Edit contact > Preferred Line, or long‑press the SIM label on the call screen.
Android: Set default SIM in the dialler or choose per call/SMS if prompted.
Data still draining on Home SIM:
iPhone: Settings > Mobile Data > turn off “Allow Mobile Data Switching”.
Android: Ensure Preferred Data SIM = Travel and Data Roaming is off on Home.
Can’t install eSIM:
Confirm your phone is carrier‑unlocked and eSIM‑capable. Reboot and retry. If travelling to the US, check compatibility with Esim United States guidance; for Europe, see Esim Western Europe.

Real‑world setups

One country, maximum simplicity:
Example: Weekend in Paris. Install a France data plan, set it as Mobile Data, keep your UK SIM for calls/SMS only. See Esim France.
Multi‑city Euro trip:
Example: Italy–Spain–France in one week. Use a regional plan so you don’t juggle multiple profiles. See Esim Western Europe or country packs like Esim Italy and Esim Spain.
North America loop:
Example: US and Canada. Use Esim North America and keep your home line for OTPs and inbound calls. If only the US, see Esim United States.
Business travellers:
Centralise policy and support so staff don’t toggle iMessage abroad or re‑register WhatsApp. Volume options are available For Business, and partners can access enablement via the Partner Hub.

Browse full coverage and plans on Destinations.

FAQ

Will people still see my usual number on WhatsApp?
Yes. WhatsApp identity stays tied to the number you registered. Using a travel eSIM only changes your data connection, not your WhatsApp number.
Do I need to use “Change Number” in WhatsApp when I travel?
No. Only use “Change Number” if you are permanently moving to a new number. For travel, keep your existing registration.
Can I remove my home SIM entirely?
You can, but you may lose access to SMS/OTP and iMessage number activation. It’s safer to keep the home line inserted and disable its data roaming. If you must remove it, set up backup codes, an authenticator app, and Apple/Google recovery options first.
Will iMessage charge me abroad?
iMessage itself uses data. However, (re)activating iMessage on a phone number can send one international SMS charged by your carrier. Activate before departure and avoid toggling while abroad.
Can I still receive SMS/OTP if data roaming is off on my home SIM?
Usually yes; SMS does not require data. Whether receiving SMS while roaming is charged depends on your carrier. Check your plan before you go.
WhatsApp asked me to verify again – what now?
Proceed only if your home number can receive the SMS/voice code. If not, wait until you have coverage or Wi‑Fi Calling, or use linked devices temporarily. Ensure two‑step verification is enabled to protect against SIM‑swap attacks.

Next step: Choose your travel eSIM and stay connected without losing your number. Start with Destinations.

Read more blogs

Andes Highlights (3 Weeks): Peru–Bolivia–Chile–Argentina Connectivity

Planning a south america itinerary 3 weeks through the high Andes? This route stitches together Peru’s Sacred Valley, Bolivia’s La Paz and Salar de Uyuni, Chile’s Atacama Desert, and northern Argentina’s quebradas or Mendoza wine country—often by long-distance bus and a couple of short flights. Connectivity is different at altitude: coverage is strong in cities but drops in high passes and salt flats; bus Wi‑Fi is patchy; border towns can be blackspots. The smart move is an eSIM with multi‑country coverage, backed by offline maps, offline translations, and a simple routine for crossing borders by bus without losing service. Below you’ll find a practical, connectivity-first itinerary; checklists to prep your phone, apps and documents; and on-the-ground tips for staying online where it matters: booking transport, hailing taxis, backing up photos, and navigating when the signal disappears.If you’re transiting via Europe or North America, you can also add a layover eSIM to stay connected door-to-door. Start with our country list on Destinations, then follow the steps, and you won’t waste time chasing SIM shops at 3,500 metres.The 3‑week Andes route at a glanceWeek 1: Peru (Cusco, Sacred Valley, Machu Picchu) - Fly into Cusco (or Lima then connect). - Base in Cusco; day trips to Pisac/Chinchero/Maras–Moray. - Train to Aguas Calientes; Machu Picchu visit; return to Cusco or continue to Puno/Lake Titicaca.Week 2: Bolivia and Chile (La Paz, Uyuni, San Pedro de Atacama) - Bus/collectivo via Copacabana to La Paz. - Fly or overnight bus to Uyuni. - 3‑day Uyuni–altiplano tour ending in San Pedro de Atacama (Chile).Week 3: Chile and Argentina (Atacama to Salta or Mendoza/Buenos Aires) - Choose: - North: San Pedro to Salta/Jujuy by bus; fly to Buenos Aires. - Or South: San Pedro–Calama flight to Santiago; bus or flight to Mendoza; onward to Buenos Aires.Connectivity notes (quick): - Cities: generally strong 4G/4G+; 5G in major hubs (Santiago, Buenos Aires). - Altitude/rural: expect long no‑signal stretches (Uyuni, altiplano passes, Paso Jama). - Bus Wi‑Fi: often advertised, rarely reliable. Plan to be offline onboard. - Border regions: networks switch; a multi‑country eSIM avoids sudden loss.eSIM vs local SIMs for a 4‑country tripFor a route with multiple borders and remote legs, eSIM wins on time and reliability.What a multi‑country eSIM gets you: - One plan across Peru, Bolivia, Chile, Argentina (check coverage per country on Destinations). - No passport/SIM registration queues at kiosks. - Keep your home number active on the physical SIM for calls/SMS codes. - Instant top‑ups if you burn data on photos or navigation.When a local SIM still helps: - Long stay in one country with heavy data use (e.g., a month in Buenos Aires). - Dead zones where a different local network performs better (rarely worth the hassle on a 3‑week pace).Practical approach: - Use an eSIM as your primary data line across all four countries. - If you find a specific local network far better in one region, add a cheap local SIM and keep the eSIM as backup.Device readiness checklist (before you fly)1) Check eSIM compatibility and SIM‑lock status on your phone.2) Buy and install your eSIM while on home Wi‑Fi. Keep a PDF/printed copy of the QR code.3) Label lines clearly (e.g., “eSIM Andes Data”, “Home SIM”).4) Turn on data roaming for the eSIM; leave roaming off for your home SIM to avoid charges.5) Set up dual‑SIM rules: data on eSIM; calls/SMS default to home SIM if needed.6) Download offline: Google Maps/Organic Maps for all target regions; language packs (Spanish at minimum); bus/air tickets; hotel confirmations.7) Cloud backups: set to upload on Wi‑Fi only; pre‑create shared albums for travel companions.8) Test tethering/hotspot with your laptop/tablet.If you’re transiting popular hubs, consider a short layover eSIM: - USA connections: add an Esim United States or a broader Esim North America.- Europe connections: Madrid/Barcelona? Use an Esim Spain. Paris or Rome? See Esim France and Esim Italy. Multi‑country layovers? Try Esim Western Europe.City‑by‑city connectivity notesCusco & the Sacred Valley (Peru)Coverage: Good in Cusco city; variable in high villages (Maras/Moray) and along Inca Trail approaches.Tips: Download Sacred Valley maps offline; pin viewpoints and ruins. most taxis use WhatsApp—save your accommodation’s number.Machu Picchu/Aguas Calientes: Patchy to none at the citadel. Upload your photos later; don’t rely on live ticket retrieval.Lake Titicaca: Puno and CopacabanaPuno: Reasonable 4G; bus terminals crowded—screenshot QR tickets.Crossing to Copacabana: Expect a signal drop around the border; have directions saved offline.La Paz (Bolivia)Good urban 4G; the cable car network has decent signal but tunnels do not.Yungas/“Death Road” tours: Mountain valleys cause dead zones—share your emergency contacts with the operator, carry a charged power bank, and don’t plan remote calls.Uyuni and the Altiplano (Bolivia to Chile)Uyuni town: OK 4G; ATMs finicky—use Wi‑Fi for banking apps.Salt flats/lagunas: Assume offline for most of the 3‑day tour. Guides often carry satellite phones; agree a pickup time/place in San Pedro and preload your map route.San Pedro de Atacama (Chile)Town: Solid 4G; accommodations often have Wi‑Fi but speeds vary.Geysers, Valle de la Luna: Offline navigation essential; sunrise trips start before mobile networks wake up in some areas.Salta/Jujuy or Mendoza/Buenos Aires (Argentina)Salta/Jujuy: Good city coverage; quebradas have long no‑signal sections.Mendoza: City 4G/5G; vineyards outside town can be patchy.Buenos Aires: Strong 4G/5G; ideal for cloud backups and large downloads before you fly home.Border crossings by bus: step‑by‑stepThe big ones on this route: Peru–Bolivia (Puno/Copacabana), Bolivia–Chile (Uyuni–San Pedro via Hito Cajón), Chile–Argentina (Paso Jama to Salta or Los Libertadores to Mendoza).How to keep service and sanity:1) The day before:- Top up your eSIM data.- Confirm your plan includes both countries you’re entering/leaving.- Download offline maps for both sides of the border and your town of arrival.- Save bus company WhatsApp and terminal address offline.2) On departure morning:- Keep a paper copy or offline PDF of tickets, insurance, and accommodation proof.- Charge phone and power bank; pack a short cable in your daypack.3) On the bus:- Don’t count on bus Wi‑Fi. Keep your eSIM as primary, but expect drops near mountain passes.- If your phone supports it, enable “Wi‑Fi calling” for later when you reach accommodation Wi‑Fi.4) At the border posts:- Data may be unavailable. Keep QR codes and booking numbers offline.- After exiting one country and entering the next, toggle Airplane Mode off/on to re‑register on the new network.- If the eSIM doesn’t attach, manually select a network in Mobile Settings.5) Arrival:- Send your accommodation a quick WhatsApp when you’re back online.- Recheck your eSIM’s data roaming is on; confirm you’re on an in‑country network, not a weak roaming partner.Pro tips: - Dual profiles: If your eSIM allows, keep a secondary profile for a different network in the same country—helpful in border towns.- Cash buffer: Some border terminals don’t accept cards; download a currency converter for offline use.Offline survival kit (5‑minute setup)Maps: Download regions for Cusco, Sacred Valley, Puno, La Paz, Uyuni, San Pedro, Salta/Jujuy or Mendoza, and Buenos Aires.Translations: Download Spanish for offline use; add phrasebook favourites (bus tickets, directions, dietary needs).Documents: Save PDFs of passports, tickets, hotel addresses; star them for quick access.Rides: Screenshots of pickup points; pin bus terminals and hotel doors.Entertainment: Podcasts and playlists for long bus legs, set to download on Wi‑Fi only.Altitude and your tech: what changesCoverage gaps lengthen: Fewer towers at high altitude; valleys can block signal. Assume offline on remote excursions.Batteries drain faster in cold: Keep your phone warm and carry a power bank (10,000–20,000 mAh).Hotel Wi‑Fi may be congested: Schedule big uploads (photo backups, app updates) for big-city stays like Santiago or Buenos Aires.GPS still works offline: Your blue dot shows on offline maps without data—preload everything.Data budgeting for 3 weeksTypical traveller usage across this route: - Messaging/Maps/Bookings: 0.2–0.5 GB/day- Social and photo sharing: 0.3–0.7 GB/day- Occasional video calls/streaming: 0.5–1.0 GB/dayFor a mixed-use trip, plan 15–25 GB for 3 weeks. Heavy creators should double it and upload over hotel Wi‑Fi when possible. If you work remotely, consider a higher‑capacity plan and a backup eSIM; see our guidance on For Business.Practical route with transport and connectivity cuesDays 1–4 Cusco base: Strong city signal; day trips may be spotty—go offline-ready.Days 5–6 Machu Picchu: Expect no service at the ruins; sync tickets ahead.Days 7–8 Puno to La Paz via Copacabana: Border signal drop; re‑register networks after crossing.Days 9–11 Uyuni tour to San Pedro: Treat as offline; charge nightly; carry spare cables.Days 12–14 San Pedro: Stable in town; tours offline; top up data before Paso Jama.Days 15–17 Salta/Jujuy or Mendoza: Good urban 4G; rural patches are offline.Days 18–21 Buenos Aires: Strongest connectivity of the trip; clear your uploads and map downloads for the flight home.Partnering and stopover extrasHospitality and tour operators in the Andes: help your guests stay connected—explore co‑branded solutions via our Partner Hub.Transatlantic flyers: test your eSIM setup on a layover with an Esim United States or Esim Western Europe before hitting high-altitude blackspots.FAQs1) Do I need a local SIM in each country?No. A multi‑country eSIM covering Peru, Bolivia, Chile and Argentina is simpler and works well for a 3‑week pace. Consider a local SIM only if you’ll spend longer in one country and want the absolute best regional coverage.2) Will my WhatsApp number change with an eSIM?No. WhatsApp is tied to your registered number, not your data line. Keep your home SIM active for voice/SMS (roaming off if you wish), and use the eSIM for data—WhatsApp continues as normal.3) Can I hotspot to my laptop or camera?Yes. Enable tethering on your eSIM. Mind your data: cloud backups and OS updates can burn gigabytes—set them to Wi‑Fi only or schedule in big cities.4) What if there’s no signal on the Uyuni/Atacama legs?That’s expected. GPS still works offline. Pre-download maps and translations, carry a power bank, and sync plans with your tour operator before departure.5) Will I get roaming charges at borders?If you’re using a multi‑country eSIM with coverage in both countries, you won’t incur extra roaming fees from your home carrier. Keep roaming off on your home SIM to avoid accidental use.6) I’m connecting via Europe or the US—worth getting a layover eSIM?Yes. It’s an easy way to test your setup and stay reachable. Try Esim North America or country options like Esim Spain, Esim France, or Esim Italy for common hubs.Next step: Browse South America coverage options and build your plan on Destinations.

31 Oct 2025

Multi-Network Smart Switching: Rollout Notes & Supported Regions

Smart, seamless coverage shouldn’t be a lottery. Our new Multi-Network Smart Switching automatically connects your Simology eSIM to the best available partner network in your location, then re-evaluates in the background as conditions change. The result: fewer dead spots, more consistent speeds, and less time fiddling with settings. This post is your single source of truth for the simology smart switching rollout: what’s live today, what’s next, supported regions/carriers, device tips, and known limitations. If you manage travellers or teams, there’s guidance for you too.We’re rolling this out region by region to ensure quality and stability. As of publication, Smart Switching is standard across key Western Europe and North America destinations, with phased expansion underway elsewhere. You’ll find a clear changelog below, plus setup steps and practical pro tips gathered from early users. For the technical deep dive (how the selection engine weighs signal, latency and cost), see our note under “Tech explainers”.What is Multi-Network Smart Switching?Smart Switching lets a single eSIM session move across multiple local partner networks in a country (and across borders) without you manually changing carriers. Instead of relying on one roaming partner, your device is guided to the best option available based on real-world conditions.What you get versus a single-network eSIM: - Higher reliability in fringe or congested areas. - Better average speeds by steering to less-loaded networks. - Smoother cross-border transitions on regional passes. - Less manual intervention—no need to lock to one network.For a technical overview of how our selection engine works, partners and resellers can find deeper notes on the Partner Hub.Rollout at a glance (changelog)We’re sharing the rollout transparently so travellers and ops teams can plan confidently.October 2025General availability in Western Europe and North America regional products.Default-on for new eSIM activations in supported countries; existing eSIMs gain it after next profile refresh.September 2025Expanded beta to France, Italy, Spain and the United States; added live failover on 4G/5G.August 2025Closed beta in select Western Europe markets; early access for enterprise groups via For Business.Note: Capability depends on local partner integrations and device support. Check the live country list on Destinations before you fly.Supported regions and partner coverageCarrier availability can change; the lists below are indicative of current partners used for Smart Switching. You may see some or all of these networks in a given location. For the latest, refer to Destinations.Western Europe (general availability)France — typical partners include Orange, SFR, Bouygues. See country detail on Esim France.Italy — typical partners include TIM, Vodafone, WindTre. See Esim Italy.Spain — typical partners include Movistar, Orange, Vodafone. See Esim Spain.Germany — typical partners include Telekom (DT), Vodafone, O2.Netherlands — KPN, VodafoneZiggo, Odido (formerly T-Mobile NL).Belgium — Proximus, Orange, BASE.Switzerland — Swisscom, Sunrise, Salt.Austria — A1, Magenta, Drei.Portugal — MEO, NOS, Vodafone.Ireland — eir, Vodafone, Three.Regional bundles — Smart Switching across multiple countries on Esim Western Europe.North America (general availability)United States — typical partners include AT&T, T-Mobile, Verizon. See Esim United States.Canada — Rogers, Bell, Telus (varies by province).Mexico — Telcel, AT&T Mexico, Movistar.Regional bundles — multi-country coverage on Esim North America.UK and nearbyUnited Kingdom — EE, Vodafone, O2, Three.Channel Islands/Isle of Man — limited Smart Switching; coverage varies by island.Nordics & Baltics (expanding rollout)Sweden, Norway, Denmark, Finland — multi-network support across major operators; 5G availability varies.Estonia, Latvia, Lithuania — multi-network support in principal urban areas; expanding to rural zones.DACH & Benelux (general availability)Covered above under Western Europe; Smart Switching generally live across these markets.Central & Eastern Europe (phased)Poland, Czechia, Hungary, Romania, Croatia, Slovenia — multi-network live in tier-1 cities; rural expansion ongoing.APAC (pilot/early access)Australia, New Zealand, Singapore, Japan — Smart Switching available on selected plans; broader rollout planned following stability testing.Middle East & Africa (early access)UAE, Qatar, South Africa, Kenya — limited Smart Switching where multiple partner networks are available; more markets coming online in phases.Device compatibility and setupSmart Switching is a network-side feature that works best when your device is allowed to choose automatically.Supported devices - iPhone with iOS 16 or newer (recommended iOS 17+). - Android devices with eSIM support, Android 12 or newer (Pixel 6+, Samsung S21+ and newer, and equivalents). - Dual-SIM devices supported; set Simology as your Data SIM.How to enable (takes 2–3 minutes) 1) Update the Simology app to the latest version. 2) Install or refresh your eSIM profile as prompted in the app. 3) On your phone: - iPhone: Settings > Mobile Data > your Simology eSIM > Turn on Data, Data Roaming; ensure Network Selection is set to Automatic. - Android (Pixel example): Settings > Network & Internet > SIMs > your Simology eSIM > Enable Mobile Data, Roaming; ensure Automatically select network is on. 4) Leave 5G/LTE set to “Auto” and VoLTE enabled (where available). 5) If you previously manually locked to a network, toggle Airplane Mode off/on to clear the lock.Quick checklist before you travel - Install your eSIM while you have good Wi‑Fi. - Toggle Data Roaming on. - Set network selection to Automatic. - Ensure APN remains default (do not edit unless instructed by support). - Keep your device updated (carrier settings included).How Smart Switching decidesOur selection engine blends network-side signals and device feedback:Availability and signal quality (RSRP/RSRQ and SINR, where reported).Measured throughput and latency from lightweight probes.Congestion indicators (time-of-day patterns, historical performance).Local policy (e.g., prefer networks with better VoLTE/5G SA coverage).Power impact (avoid aggressive flapping; minimum dwell times apply).It’s designed to be conservative—fewer, smarter switches rather than constant hopping. If you need to hold a network temporarily (e.g., for a live upload in a strong cell), you can manually select it; Smart Switching resumes when you return to Automatic.For partner-facing logic and scoring weights, see the integration notes on Partner Hub.Benefits versus a single-network approachReliability: Better building penetration in one area? You’re steered there. A festival saturates a cell? We move you off it.Speed consistency: The “best” network changes by street and time; Smart Switching adapts without you intervening.Cross-border ease: On regional passes, your device hands over cleanly when you cross into the next country.Fewer support headaches: No more “try another network” back-and-forth—your eSIM tests options automatically.Traveller-first: Works quietly in the background; you focus on your trip.Pro tips from early travellersUse Airplane Mode as a soft reset: if speeds dip, toggle it for 10 seconds to force a quick re-evaluation.Keep 5G on Auto: forcing 5G-only can backfire in patchy areas; Auto lets us pick LTE when it’s faster.Don’t edit APN: custom APNs can break switching logic; stick with the default profile.Hotspotting: tethering works, but heavy hotspot sessions can delay switching while we protect session stability.VPNs: Smart Switching works fine with VPNs; if you see unusual latency, test briefly without the VPN to isolate issues.Border crossings: you may see “No Service” for 10–30 seconds while the device updates network credentials—this is normal.For teams and partnersBusiness rollouts: Admins can enable Smart Switching at account or group level, apply country policies, and review network experience metrics in dashboards. Learn more on For Business.Resellers/partners: API flags and webhooks are available for status, preferred network lists, and policy overrides. Documentation lives on the Partner Hub.Known limitations and workaroundsData-first: Simology eSIMs are data-only. For voice/SMS and emergency calling, keep a native line active on your device.Minimum dwell times: To avoid flapping, we wait a short period before switching again unless the current connection is unusable.Country variability: Some countries restrict multi-network roaming; Smart Switching may behave like single-network there.Older devices: Certain chipsets report incomplete metrics; switching still works but may be less dynamic.2G/3G sunsets: In markets where legacy networks are retired, voice fallback depends on VoLTE support on your primary line.Enterprise firewalls: If using strict VPNs or private DNS, allow our lightweight probing to ensure accurate performance reads.simology smart switching rollout: where to startIf you’re travelling in Western Europe or North America, Smart Switching is already included on current regional plans like Esim Western Europe and Esim North America, as well as popular single-country packs such as Esim France, Esim Italy, Esim Spain, and Esim United States. Outside these regions, check your specific country page on Destinations for live status.FAQQ: Does Smart Switching cost extra? A: No separate app fee. It’s included on most current regional and supported single-country eSIMs. Check your plan page on Destinations to confirm availability for your chosen country.Q: Can I force a specific network? A: Yes. You can manually select a network in device settings. We recommend returning to Automatic afterwards so Smart Switching can optimise as conditions change.Q: Will this drain my battery? A: No significant impact. We rely on network-side data and lightweight device probes, with minimum dwell times to avoid constant reselection.Q: Is 5G supported? A: Yes, where partner networks provide 5G. Smart Switching may choose LTE if it’s faster or more stable in your location.Q: How do I see which network I’m on? A: Your status bar shows the current network name. The Simology app also displays the active network and recent switches in the connection details.Q: Is it available on business accounts? A: Yes. Business admins can enable it per group or policy and review network experience analytics. See For Business for rollout options.Need help?Check your destination’s live status and supported carriers via Destinations.In the app, run “Connection Check” and follow any suggested fixes.If issues persist, share your location, device model, and a short description of what you see (e.g., “drops to 3G indoors in Lyon”) with support—we’ll review the network log and adjust policy if needed.Next stepPlanning a trip? See where Smart Switching is live and pick the right eSIM on Destinations.

30 Oct 2025

VoLTE & Wi‑Fi Calling Abroad: Make Calls Reliably on eSIM

If you travel with an eSIM, two features determine whether your calls “just work”: VoLTE (Voice over LTE) and Wi‑Fi Calling (VoWiFi). Both let you place normal voice calls without falling back to old 3G/2G networks. That matters because many countries have retired 3G and some are winding down 2G; in the United States, for example, VoLTE is essential for voice. This guide explains how to set up and troubleshoot VoLTE and Wi‑Fi Calling abroad, especially when you’re using a data‑only travel eSIM and want your home number reachable. We’ll cover carrier prerequisites, dual‑SIM line selection, roaming toggles, and practical fixes for the common pitfalls travellers hit. If you only skim one section, make it the “Set‑up recipes” and the troubleshooting tree. For destination specifics and compatible plans, browse our regional eSIMs, including Esim United States, Esim Western Europe and Esim North America, or explore all Destinations.What VoLTE and Wi‑Fi Calling mean when you roamVoLTE: Your phone makes standard cellular calls over 4G/LTE (or 5G) networks using IMS. It’s required in markets where 3G is shut down (e.g., USA). Without VoLTE support on the visited network, calls may fail or drop.Wi‑Fi Calling (VoWiFi): Your carrier routes your normal phone number over any Wi‑Fi or mobile data connection. Abroad, this lets your home number ring even if you’ve disabled roaming on your home SIM. Think of it as “your number, over the internet”.How this plays with eSIM: - Most travel eSIMs are data‑only. You keep your home SIM for your number and use Wi‑Fi Calling over your eSIM’s data. - If you buy a local eSIM with voice, you’ll use VoLTE for direct cellular calling in country. Ensure that plan and your device are VoLTE‑enabled on the visited network.Pro tip: For the US, prioritise VoLTE‑capable devices and plans; see Esim United States. For multi‑country trips, check regional coverage like Esim Western Europe and Esim North America.Prerequisites: what must be true for calls to workBefore boarding, confirm the essentials based on how you’ll call.If you’ll keep your home number via Wi‑Fi Calling over a travel eSIM (most common)Your phone supports Wi‑Fi Calling and it’s enabled on your home carrier account.Your home carrier allows Wi‑Fi Calling while abroad. Many do; some restrict it by country or plan.You can receive an SMS while on Wi‑Fi (needed for banking/2FA). Some carriers only deliver SMS over cellular; check before you rely on it.Your travel eSIM provides a stable data connection (4G or better).You know how to set “Default Voice Line” (iPhone) or “Preferred SIM for Calls” (Android) to your home SIM.If you’ll use a local eSIM for voice via VoLTEThe eSIM plan includes voice service (many travel eSIMs are data‑only).Your phone supports VoLTE on the visited carrier’s bands.The eSIM/carrier has provisioned IMS/VoLTE on your line.You’ve enabled VoLTE in device settings and allowed voice roaming.For the US: No 3G fallback; without VoLTE your calls won’t work.Planning resources: - Country pages highlight network specifics and plan types: Destinations - Popular country packs with excellent LTE coverage: Esim France, Esim Italy, Esim SpainSet‑up recipes that just workRecipe A: Keep your home number alive with Wi‑Fi Calling over a data eSIMThis gives you cheap local data and your usual number for incoming/outgoing calls and SMS.iPhone (iOS 16/17): 1. Install and activate your travel eSIM. Confirm data works. 2. Settings > Mobile Data: - Mobile Data: select your Travel eSIM. - Turn on Data Roaming for the Travel eSIM. - For your Home SIM: keep Data Roaming OFF to avoid charges. 3. Tap Default Voice Line: set it to your Home SIM. 4. Wi‑Fi Calling: Settings > Phone > Wi‑Fi Calling > On (for Home SIM). If your carrier presents a terms screen, accept/verify. 5. Allow Mobile Data Switching: - Recommended: ON. iPhone will use data from your Travel eSIM to support calls on your Home SIM, without using home data roaming. - Safety check: keep “Data Roaming” on the Home SIM OFF, so switching cannot trigger paid roaming. 6. Make a test call with Wi‑Fi or strong 4G data. You should see “Wi‑Fi” or “Wi‑Fi Calling” in the status.Android (Pixel/Samsung/OnePlus – wording varies): 1. Install and activate your travel eSIM. Confirm data works. 2. Settings > Network & Internet > SIMs: - Mobile Data: Travel eSIM. - Data Roaming: ON for Travel eSIM; OFF for Home SIM. - Preferred SIM for Calls: Home SIM. 3. Wi‑Fi Calling: Settings > Wi‑Fi Calling > On for Home SIM. - Calling preference: Prefer Wi‑Fi (or Wi‑Fi preferred) if available. 4. Optional: “Use SIM data for calls on other SIM” or “Dual SIM data switching” ON, if available. It will use Travel eSIM data to sustain Home SIM calls. 5. Test an inbound and outbound call.Pro tips: - Keep the Phone app’s line selector visible before dialling so you don’t accidentally place a call on the travel eSIM. - If SMS over Wi‑Fi isn’t supported by your home carrier, briefly enable home SIM cellular (still with data roaming OFF) to receive 2FA codes.Recipe B: Use a local eSIM for native voice via VoLTEUse this if your eSIM includes minutes or you need a local number.All devices: 1. Confirm the eSIM plan includes voice. 2. Settings > Mobile/Cellular > enable VoLTE/4G Calling for that line. 3. Enable Voice Roaming if you plan to cross borders within the plan’s region (e.g., EU). 4. Network mode: 4G/5G Auto. Avoid 3G/2G‑only modes. 5. Place a test call. Check the status bar shows 4G/VoLTE during the call (not “3G/ H/ E”).If calls drop to 3G or fail: - Update carrier settings (iPhone prompt) or install the APN/IMS config provided. - Reboot; re‑insert eSIM if needed. - Manually select a different partner network in the same country.Country specifics and planningUnited States: 3G is shut down; VoLTE is mandatory for cellular calling. If your phone or plan doesn’t do VoLTE on the visited network, use Recipe A (Wi‑Fi Calling over data) as your fallback. See Esim United States.Canada, Mexico and USA trips: plan for cross‑border behaviour and partner networks. Check Esim North America.Western Europe: Broad VoLTE support and EU‑wide roaming on many plans. Recipe A works well for keeping your home number; Recipe B is easy if your eSIM includes voice. See Esim Western Europe.Popular single‑country picks with strong LTE: Esim France, Esim Italy, Esim Spain.Travelling as a team? Centralise setup guidance and plan choice via For Business or coordinate with your reseller through our Partner Hub.Troubleshooting tree: call fails or drops when abroadStart with your scenario and follow the checks in order.1) My home number doesn’t ring; I’m using a data eSIM - Is Wi‑Fi Calling enabled on the home SIM? Turn it on. - Can your device reach data? Open a web page; if not, fix data/APN first. - Carrier allows Wi‑Fi Calling abroad? If unsure, test on hotel Wi‑Fi; if it only works on your home ISP, your carrier may restrict it. - iPhone: Allow Mobile Data Switching ON; Home SIM Data Roaming OFF. - Android: Wi‑Fi Calling preference = Prefer Wi‑Fi; Dual SIM data switching ON (if available). - Still no joy: toggle Airplane Mode ON then enable Wi‑Fi only; try calling. If it now works, your carrier might prioritise Wi‑Fi Calling when cellular is off.2) Calls fail in the USA on a local SIM/eSIM - Confirm the line supports VoLTE on that network. - Device: VoLTE/4G Calling ON; network mode 4G/5G. - If calls drop to 3G or never connect, switch to a different partner network or use Recipe A as a fallback.3) I can call but SMS 2FA won’t arrive - Some carriers don’t deliver SMS over Wi‑Fi. Temporarily allow the home line to register on cellular (keep Data Roaming OFF) to receive codes. - Ask your bank to enable app‑based or email 2FA as a travel workaround.4) Calls use the wrong line - Set Default Voice Line (iPhone) or Preferred SIM for Calls (Android) to the correct SIM. - Before dialling, check the SIM selector in the Phone app; on iPhone, long‑press the call button to switch lines.5) Wi‑Fi Calling toggles are missing - Your carrier or device may not support it, or it’s not provisioned. Update carrier settings/OS, or contact your carrier to enable. - Some countries restrict VoIP/Wi‑Fi Calling; try a different network/Wi‑Fi.6) Audio is poor or calls drop on Wi‑Fi - Switch Wi‑Fi to 5 GHz, or move closer to the router. - Turn off VPN; some VPNs break IMS traffic. - Disable battery/data savers that restrict background data.Pro tips and gotchasPrefer Wi‑Fi Calling for long international calls. It uses your home plan’s domestic rates for many carriers, but always check your tariff.Avoid bill shock: keep Data Roaming OFF on your home SIM. You can still use Wi‑Fi Calling via the travel eSIM’s data if mobile data switching is enabled.In dual‑SIM mode, iPhone can show “Primary” and “Secondary”; rename them to “Home” and “Travel” so you don’t mis‑dial.Emergency calls: Wi‑Fi Calling may not route accurately abroad. Know the local emergency number and, where possible, place emergency calls over the local cellular network.US travellers: bring a VoLTE‑ready device. Older handsets that relied on 3G voice won’t work for calling.Business itineraries: standardise a setup playbook (Recipe A) for your team and test before departure. See For Business.FAQsQ: What’s the simplest way to keep my number when I use a travel eSIM? A: Use Wi‑Fi Calling on your home SIM over your travel eSIM’s data (Recipe A). Set your travel eSIM as the data line, keep data roaming off on the home SIM, and enable Wi‑Fi Calling.Q: Do all travel eSIMs support voice calls with VoLTE? A: Many travel eSIMs are data‑only. If you need native voice, choose an eSIM that explicitly includes minutes/voice and make sure VoLTE is supported in your destination.Q: Will Wi‑Fi Calling work in every country? A: Not always. Most carriers support it internationally, but some restrict usage by location or plan. A few countries and networks limit VoIP/Wi‑Fi Calling. Test on both Wi‑Fi and mobile data at your destination.Q: My SMS codes aren’t arriving while abroad. Why? A: Some carriers don’t deliver SMS over Wi‑Fi Calling. Temporarily register your home SIM on cellular (with data roaming off) to receive them, or switch to app‑based 2FA.Q: In the USA, my calls fail on a local SIM. What now? A: You likely need VoLTE on that network. Enable VoLTE/4G Calling, set network mode to 4G/5G, and try another partner network. If still failing, use Wi‑Fi Calling over your travel eSIM’s data as a fallback. See Esim United States.Q: How do I avoid using the wrong SIM for calls or data? A: Set your Default Voice Line/Preferred SIM for Calls to your chosen number, and your Mobile Data line to the travel eSIM. On iPhone, consider turning on “Allow Mobile Data Switching” with data roaming off on your home SIM to stay safe.The quick checklistsBefore you fly: - Update iOS/Android and carrier settings. - Confirm Wi‑Fi Calling is enabled on your home SIM and supported abroad. - Decide your calling method: Wi‑Fi Calling over data (Recipe A) or local voice via VoLTE (Recipe B). - Verify your device is VoLTE‑ready for the region (critical for the USA). - Save our destination links: Destinations, Esim Western Europe, Esim North America.On arrival: - Activate data on your travel eSIM; test browsing. - Set line selection: Data = Travel eSIM; Calls = Home SIM (if using Recipe A). - Enable Wi‑Fi Calling for the line you’ll use to call. - Place a short test call and send yourself a test SMS.Next step: choose the right regional plan and follow the setup recipe for your device. Start with Destinations to pick your eSIM for the country or region you’re visiting.

30 Oct 2025