Wi-Fi Calling abroad, explained

Your number, your Phone app, a different road

With Wi-Fi Calling on, you dial from the usual Phone app and the person you call sees your normal number. Nothing about the call looks different to them. The only change is the path: instead of going through a mobile mast, the call travels over the Wi-Fi network you are connected to and reaches your operator through the internet.

Apple's documentation says that when it is active, Wi-Fi appears next to your carrier name in the status bar. Google's Phone app shows Internet Call or Wi-Fi calling on the notification screen. That is the quickest way to tell which road a call is taking.

This is different from calling through WhatsApp or FaceTime. Those apps use their own accounts and only reach people who have the same app. Wi-Fi Calling reaches any phone number, landlines included, because it is a real call on your line.

It belongs to your home operator

Apple states that Wi-Fi Calling is not available with all carriers or in all countries or regions, and tells you to contact your carrier to confirm it. Google's help is just as direct: if the Wi-Fi calling option does not appear in your SIM settings, your carrier does not support the feature, and you may incur additional charges for calls over Wi-Fi.

So before relying on it on a trip, ask your operator three things. Does my plan include Wi-Fi Calling? Does it work while I am in another country? And is a call made over Wi-Fi from abroad billed as a domestic call, a roaming call or something else? The answers differ from one operator to another, and sometimes from one plan to another within the same operator.

How to turn it on

• iPhone: Settings, then Cellular or Mobile Data, choose your line if you have two, tap Wi-Fi Calling and turn on Wi-Fi Calling on This iPhone, then tap Enable.
• Android phones using Google's Phone app: Settings, then Network and internet, SIMs, your carrier's SIM, and turn Wi-Fi calling on.
• Other Android brands place it in their own SIM or mobile network menus; typing Wi-Fi calling in the settings search usually finds it.

On iPhone you may be asked to enter or confirm an address for emergency services. Turn it on at home, where you can make a test call and contact your operator if the switch is missing or greyed out.

Does it run over a travel eSIM's data?

Do not count on it. Apple describes a dual SIM setup in which one line uses the other line's mobile data, with Allow Cellular Data Switching turned on, and the status bar shows that line with Wi-Fi Calling enabled. In the same article, Apple warns that this cellular data switching does not work while you are using Data Roaming.

A travel eSIM normally needs data roaming switched on, because it connects to a network that is not its home one. In practice, then, plan your Wi-Fi Calling around real Wi-Fi networks: the hotel, the flat, a café. If it happens to work over mobile data on your phone and operator, treat it as a bonus and test it before you depend on it.

The small print that matters abroad

Apple notes that not all Wi-Fi networks work with Wi-Fi Calling, so a hotel network that blocks it is not a fault in your phone. If the Wi-Fi drops during a call, Apple says the call switches automatically to your operator's mobile network using VoLTE where available. Abroad, that means your home line carries the rest of the call as a roaming call.

Emergency calls follow their own rules. Apple says the iPhone uses mobile service for them when it is available, and may use Wi-Fi Calling only if there is no mobile service; it also warns that while on Wi-Fi Calling the phone may not receive emergency alerts. Keep that in mind in places where alerts matter, and call emergency numbers from the Phone app, never from a messaging app.