Three has begun rolling out a new Wi-Fi calling service to its customers, so long as they have a compatible smartphone. Wi-Fi calling is nothing new to Three, since it has been offering the function through the inTouch app, but the experience through that left a lot to be desired.

The app-free function is available for Android and iOS smartphones and will allow you to still make phone calls and send text messages in areas where you don't have phone signal, but do have a Wi-Fi signal. The London Underground for instance. You'll need to make sure you have the latest phone software and carrier settings installed on your device, and when you have the function enabled, the carrier message in the top left of your screen will change to 'Three WiFi Call'.

The feature is only compatible with certain phones though. Supported iOS devices include the iPhone 5c, 5s, 6, 6s, SE and 7, while supported Android devices include the LG G5, Samsung Galaxy S6 and S6 edge, with support for the S7 and S7 edge coming in mid-February.

Anyone using one of these devices that previously used the inTouch app will be greeted with a pop up message telling them they can delete it.