Dual SIM with a travel eSIM: keep your home number, use cheap data and avoid roaming charges

The short answer: which line does what

Once the travel eSIM is installed, each setting has a clear owner:

If you set it up like this, messaging apps keep using your usual number, SMS codes from your bank still arrive, and all data runs over the prepaid travel plan. The rest of this guide explains why each setting matters and what can still cost money.

How dual SIM works on a modern phone

Most smartphones sold in recent years can run two mobile lines at once. The combination depends on the phone:

• Physical SIM plus eSIM: the classic setup for travel. Your home SIM card stays in the tray and the travel plan is added as an eSIM.
• Two eSIMs: newer phones can keep two eSIMs active, which is how it works on iPhones without a SIM tray, such as US models since the iPhone 14.
• More profiles than lines: a phone can store several eSIMs, but only two lines are active at the same time. Switching between stored eSIMs is done in the settings.

Almost all of these phones use dual SIM dual standby: both lines wait for calls and messages, but they share one radio. In practice that means two things. While you are on a phone call on one line, the other line usually cannot take a call. And only one line can carry your mobile data at any time, which is why you choose a data line in the settings.

Not sure your phone supports eSIM at all? Our compatibility guide shows how to check, and what is an eSIM explains the basics.

The settings on iPhone

1. Labels: in Settings → Mobile Service (Cellular in some regions), give the lines clear names such as "Home" and "Travel".
2. Default voice line: choose your home line, so calls and SMS go out from your usual number.
3. Mobile data: choose the travel line after you land. Leave "Allow Mobile Data Switching" off, so the phone does not move data back to the home line on its own.
4. Data roaming per line: tap the travel line and turn Data Roaming on; tap the home line and make sure Data Roaming is off.
5. iMessage and FaceTime: in Settings → Messages and Settings → FaceTime, keep your home number selected for sending and receiving.

The step-by-step installation, with screenshots of each screen, is in our guide to installing an eSIM on iPhone.

The settings on Android

The menu names differ by manufacturer, but the choices are the same. On Samsung they are under Settings → Connections → SIM manager, on Google Pixel under Settings → Network & internet → SIMs.

1. Calls and SMS: set both to your home SIM.
2. Mobile data: set it to the travel eSIM after you land, and turn off automatic data switching if your phone offers it.
3. Roaming: on the travel eSIM, allow roaming; on the home SIM, keep data roaming off. On Pixel the roaming switch is in each SIM's own settings; on Samsung it is under Mobile networks and applies to the SIM used for data.

Detailed menus for Samsung, Pixel and other brands are in our guide to installing an eSIM on Android.

What your home number can still cost abroad

Switching off data roaming on the home SIM stops the expensive part, but calls and texts on your home number are still billed by your home carrier under its roaming rules:

• Within the EU and EEA: if your home SIM is from an EU or EEA country, calls and SMS are usually charged like at home when you travel within the region.
• Outside your carrier's roaming zone: outgoing calls and SMS are often charged per minute or per message, and on many tariffs you also pay to receive calls.
• Receiving SMS: on most tariffs this is free, also abroad, so bank codes cost nothing to receive.
• Voicemail: on some tariffs a call you do not answer abroad is forwarded to your voicemail and billed like a roaming call. Many travellers switch voicemail or call forwarding off before a long trip, through the carrier's app or, on most networks, with the code ##002#.

Your carrier's roaming page or app shows the rates for your destination. How these costs compare with a travel eSIM and a local SIM card is covered in eSIM vs roaming vs local SIM.

Bank codes, WhatsApp and iMessage abroad

The question most travellers have is whether they will still be able to log in to their bank. With the setup above, yes:

• SMS codes are sent to your number, so they arrive on the home SIM as long as that line is switched on and has network coverage. They do not need data roaming.
• WhatsApp, Signal and Telegram are linked to your phone number when you register, not to the SIM that carries the data. They keep your usual number and use the travel eSIM's data.
• iMessage and FaceTime also keep your number and run over whichever line provides mobile data.
• Banking and authenticator apps that work with app confirmations instead of SMS only need internet, which the travel eSIM provides.

One caution: do not switch the home line off completely if you expect SMS codes during the trip. Switching it off saves battery but means codes only arrive once you switch it back on.

Wi-Fi calling: take calls on your home number over the internet

Many carriers support Wi-Fi calling, which lets your home line make and receive normal calls and SMS over an internet connection instead of the mobile network. Abroad this can be useful: when the phone is on Wi-Fi, calls to your home number can come in over Wi-Fi.

Whether it works abroad and how calls are billed depends on your carrier. Some charge Wi-Fi calls like calls from home, others block Wi-Fi calling in certain countries. Turn it on before you leave (on iPhone in the settings of the home line, on Android in the call or SIM settings) and check your carrier's conditions for use abroad.

Common problems with two lines and how to fix them

• No internet although the eSIM shows signal: mobile data is still set to the home line, or data roaming is off on the travel line. Our troubleshooting guide goes through all the fixes.
• Unexpected roaming charges: data roaming was on for the home SIM, or the phone switched data to the home line automatically. Turn both off.
• Calls fail when you dial out: the phone tries to call over the data-only travel eSIM. Set the home line as the default voice line, or choose the line for each call.
• Messages go out from the wrong number: check the sending number for iMessage, and on Android the default SMS line.
• SMS codes do not arrive: make sure the home line is switched on and registered on a network; airplane mode or a switched-off line blocks them.

Before your next trip, compare plans for your destination on our destination pages, and install the eSIM a day or two before departure as described in when to activate an eSIM.