How to call home when your eSIM only has data

Two kinds of call on the same phone

When you travel with a data eSIM, your phone ends up with two ways of calling. Your usual line still makes and receives normal calls on your number, under whatever roaming terms your contract has. The travel eSIM, which only carries data, makes internet calls through apps, and those use data rather than minutes.

Most of the time the second kind is the one you want, because it does not touch your roaming allowance. The catch is that an internet call is between two apps, not two phone numbers. Your sister with WhatsApp is reachable that way; the dentist's landline is not. Knowing in advance which of the people you will need to call are which saves you surprises.

What runs over the eSIM's data

WhatsApp says its voice calls use your phone's internet connection rather than your mobile plan minutes, that they are free even when the other person is in another country, and that data charges may apply depending on your provider. Group calls take up to 32 people. With a prepaid data eSIM, the data comes out of the pack you already paid for.

On Apple devices, FaceTime audio and video calls work over Wi-Fi or mobile data, and Apple notes that data rates may apply and that FaceTime may not be available in every country or region. Other messaging apps with a call button work the same way: they need internet at both ends and the app installed at both ends. Your WhatsApp account keeps working on your usual number, as our WhatsApp guide explains.

What does not work over data alone

• Calling a landline or a mobile that does not have the same app.
• Receiving a normal phone call on the eSIM, since it has no number to call.
• Sending or receiving SMS through the eSIM, including verification codes.
• Calling emergency services from a messaging app.

For the first three, your usual line is still in the phone. Calls and texts to your number keep arriving there, and inside the EU receiving them costs nothing extra under the roaming rules. Making a call on that line abroad follows your operator's roaming terms, so ask before a long one outside the EU.

Emergency calls go through the Phone app

WhatsApp's terms state that its services do not provide access to emergency services, and that you should make sure you can reach them through a mobile phone, a landline or another service. Do not plan on an app call if something goes wrong.

Use the phone's own dialler instead. Apple says that if your carrier's network is unavailable, the iPhone tries to route emergency calls through other networks, if available. In the EU the number is 112, which the European Commission describes as free of charge everywhere in the EU, reachable from fixed and mobile phones, and also used in some countries outside the EU. Your usual line, kept installed alongside the travel eSIM, means you always have a real number in the phone.

Before you leave: test it on mobile data

Internet calls feel the same on Wi-Fi and on mobile data, but only one of them is what you will have in the street. Before the trip, switch Wi-Fi off and make a short WhatsApp or FaceTime call over your normal mobile data. If it works, the app is set up and allowed to use mobile data; on iPhone that permission is per app, under the mobile data settings.

Then think about volume. A few voice calls a day use little, but long video calls add up, and so does a call on a laptop sharing your phone's connection. Our data calculator works out a pack from your daily use, video and hotspot; if you expect long video calls, count them in the video question.