From the help page:
If you are using a Sony XZ Premium, XZ1 or XZ1 Compact, to get Wifi and 4G Calling, your device will need to use O2 firmware. This is essentially the software that makes your device turn on and run. Sometimes there are different versions of firmware for the same device. Your device should use O2 firmware if you bought it direct from us in an O2 shop, online or over the phone.
To check if your Sony is running O2 firmware:
Open the ‘Chrome’ app and tap the Home icon in the top left corner. If this takes you to
www.o2.co.uk then your device has O2 firmware. If it takes you to Google, then Wifi and 4G Calling isn’t supported on your phone right now.
If you have changed the homepage in Chrome since buying your device, tap the three dots in the top right corner of Chrome, tap Settings, tap homepage, tap to edit the homepage and then press ‘Reset’. If it resets to
www.o2.co.uk, then your device has O2 firmware. If it resets to Google, then Wifi and 4G Calling isn’t supported on your phone right now.
If you need more info, contact us