Wi-Fi calling
Wi-Fi calling will be great news for passengers on the London Underground iStock

Three UK has launched embedded Wi-Fi calling on its mobile network, allowing customers to send and receive calls and messages when they have no mobile signal by hopping on Wi-Fi networks. The operator joins rivals EE and Vodafone in offering the service 'natively' – without the need for an app.

The main advantages of this is better indoor coverage, the ability to receive calls and texts when under ground (on the Tube in London or another Metro network, for example) and even in the air on planes that offer in-flight Wi-Fi. Technically speaking, Three has offered Wi-Fi calling for years, but until now this was only been available through its Three InTouch app, which needs to be running in the background when users wish to make a call over a Wi-Fi network.

From 31 January, this is no longer necessary: whenever you're somewhere where there's no mobile signal, provided there's a WLAN network to connect to, your phone will automatically route calls through Wi-Fi instead.

While Wi-Fi calling on rival network EE is only available for pay-monthly customers, a Three spokesperson told IBTimes UK that its service is available for contract, SIM-only and pay-as-you-go subscribers.

At launch, compatible smartphones include the LG G5, Samsung Galaxy S6 and S6 Edge, and the iPhone iPhone SE, 5c, 5s, 6, 6s and 7. The Samsung Galaxy S7 and S7 Edge are to be compatible from the middle of February.

Android users need to ensure they have the latest software version (Nougat) installed on their device, but other than that Wi-Fi calling will be automatically activated, Three said. iPhone users need to have iOS 10.2 or above installed and then go to 'Settings>Phone>Wi-Fi Calling' and switch the feature on manually. "Three WiFi Call" will appear in your phone's notification bar when you're connected to a Wi-Fi call.