You want an eSIM for data abroad and your own number for calls. You want the home SIM unable to run up a roaming bill, and you want WhatsApp to keep working. Most phones from the last few years with eSIM can do all of that at once. Below is the setup, screen by screen, for iPhone and Android, plus what happens to WhatsApp and bank codes, and the one switch that matters most.
What dual SIM actually means
Every iPhone since the XS and XR, every Pixel since the 3a and every Samsung flagship since the S20 can hold two lines at the same time: one physical SIM plus one eSIM, or on newer phones two eSIMs. Both lines are live together. Both numbers ring. You choose which one carries data, which one is the default for calls, and which one each contact uses.
For travel, the setup is always the same split. Your home SIM stays on for calls and texts, because that is where your number lives and where the bank sends its codes. A travel eSIM carries all the data, because local data is cheap and roaming data is not. The home SIM's data is switched off at the roaming level, so it cannot cost anything even if an app tries.
The one thing to check firstBefore anything else: your phone must be carrier unlocked to accept a second line from another provider. A phone still being paid off on a contract is often locked. iPhone: Settings, General, About, scroll to Carrier Lock. It should say No SIM restrictions. Our unlock check guide covers Android and what to do if it is locked.
iPhone: the exact settings
- Install the travel eSIM on home WiFi before you fly. Settings, Cellular, Add eSIM, scan the QR code or use the details provided. Give it a label like Travel. Leave Turn On This Line off for now.
- Home SIM roaming off. Settings, Cellular, tap your home line, Data Roaming off. This is the switch that stops the bill.
- On landing, Settings, Cellular, tap the Travel line, Turn On This Line. Then on the same screen, Data Roaming on for the Travel line only. Travel eSIMs need roaming on because they are technically roaming everywhere.
- Settings, Cellular, Cellular Data, choose Travel. Switch Allow Cellular Data Switching off, so the phone can never fall back to the home SIM for data.
- Settings, Cellular, Default Voice Line, keep it on your home line. Calls go out from your number and come in on it.
- Optional: Settings, Cellular, scroll down, switch Wi Fi Assist off. It stops the phone topping up weak WiFi with cellular.
That is all. The status bar will show two signal indicators. Messages and calls arrive on your home number, every byte of data goes through the eSIM. No bars on the Travel line after a minute? Toggle airplane mode once, then work through the not working checklist.
Android: Samsung and Pixel
- Install the eSIM on home WiFi. Samsung: Settings, Connections, SIM manager, Add eSIM. Pixel: Settings, Network and internet, SIMs, Add SIM. Label it Travel and leave it switched off.
- Home SIM roaming off. SIM manager or SIMs, tap the home line, Data roaming off.
- On landing, switch the Travel line on in the same menu, and turn Data roaming on for the Travel line.
- In SIM manager or SIMs, set Mobile data to Travel and Calls and Messages to your home line.
- So the phone does not switch lines on its own: on Samsung, turn Data switching off in SIM manager, under More SIM settings on some models. On a Pixel, turn Automatic data switching off under SIMs.
Menu names move a little between brands and Android versions, but the three controls are always there: which line has data, which line makes calls, and the roaming toggle on each. The setup guide has screenshots for the current versions.
What happens to WhatsApp
Nothing. WhatsApp, Signal, Telegram and iMessage stay tied to your home number and simply use the eSIM's data. Do not register the eSIM number in WhatsApp. Our guide to calls, texts and WhatsApp on a data only eSIM covers the rest, including how to reach a taxi or a restaurant.
The eSIM number does not matterYour travel eSIM usually has no phone number at all, or a number you will never use. That is normal. It is a data line. Every app that uses your number keeps using your home number, because the home SIM is still in the phone and still switched on.
Bank codes, and whether receiving texts costs money
Bank and airline codes come by text to your home number, so keep that line switched on with data roaming off and they arrive as normal. If one still does not come, our fix for bank codes not arriving abroad goes through the causes.
Does receiving it cost money? Usually not. AT&T rates a received text as domestic, and T-Mobile includes texting abroad on most plans. Verizon's pay as you go rate is 5 cents per received text. EU carriers charge nothing extra inside the EU. UK networks mostly let you receive texts free abroad, though some add a daily roaming fee once you use data, call or send a text. Incoming calls are a different story: on a $12 a day pass, answering a call can start a charged day, and on pay per use tariffs it costs per minute. Let unknown calls go to voicemail and call back on WhatsApp. Check your own carrier's page for the exact trigger list, because this is where plans differ.
| What you want | Which line | Setting |
|---|---|---|
| Bank and airline codes by text | Home SIM | Line on, Data Roaming off |
| Maps, WhatsApp, photos, everything data | Travel eSIM | Cellular Data line, Data Roaming on |
| Make a call to a local restaurant | Either | Tap the line icon in the dialler before dialling |
| WhatsApp, iMessage, Signal | Unchanged | Nothing to do, they follow your home number |
| No roaming bill ever | Home SIM | Data Roaming off, Cellular Data Switching off |
| Hotspot for a laptop | Travel eSIM | Personal Hotspot uses the data line automatically |
Calling out: which line dials
With two lines, the phone asks which one to use for a new call unless you set a default. Keep the home line as default so your number shows to people who know it. For a local call abroad, an eSIM with no voice service cannot dial at all, and calling a local number from your home SIM costs roaming rates. The practical answer is to call local numbers on WhatsApp where you can, and for the rare real call, use the home SIM and accept a minute of roaming. Our calls and texts on a data only eSIM guide goes through the options, including cheap internet calling apps for landlines.
When one SIM is still better
If your trip is a month or more in one country, a local SIM with a local number is cheaper per gigabyte and lets locals call you, and the airport SIM guides on this blog say so plainly. The trick is that the dual SIM setup works with a local SIM too: put the local SIM in the physical slot, keep your home number as an eSIM, or the other way round. The split is the same, only the data line changes. And if you are moving through several countries, a regional or global eSIM beats a new SIM at every border.
Home SIM plus travel eSIM: short answers
Can I use an eSIM and my physical SIM at the same time? Yes, on any iPhone from the XS on and most recent Android phones with eSIM. Both lines are live together.
Will I get charged roaming on my home SIM? Not if Data Roaming is off on the home line and Cellular Data Switching is off. Incoming texts are free on most carriers. Answering calls can cost, so let unknown calls go to voicemail.
Does WhatsApp still work with a travel eSIM? Yes, exactly as before, on your home number. Do not register the eSIM number.
Which line should be my default? Home line for voice, so your number shows. Travel eSIM for data.
Can I have two eSIMs instead of SIM plus eSIM? Yes on iPhone 13 and later and most recent Android flagships. Same settings, both lines are eSIMs. The eSIM transfer guide covers moving your home line to eSIM first.
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