16-12-2018 09:01 - edited 16-12-2018 09:11
Have a look at this thread. Plenty of help in here https://community.o2.co.uk/t5/How-to-Guides/All-you-need-to-know-about-O2-Voicemail-901/ba-p/547712
You need to set youe VM number to 901
Please note, you can only use call forwarding if you are on a pay monthly contract.
If you have problems and Wifi calling on your phone, you need to turn it off ...
on 16-12-2018 09:28
WiFi calling option can be found under your device details in your MyO2.
OnePlus 6 (O2 & Sfr), Z3 Tablet (Three UK), iPhone 8+ (EE)
on 16-12-2018 09:39
Have you actually got WiFi calling on your phone? What device is it?
If you haven't got it then it's pointless looking for it.
However, if you DO have it , it will be under DEVICE DETAILS on your phone.
16-12-2018 09:49 - edited 16-12-2018 09:53
If WiFi calling set to ON, then just move the toggle to Off...
All explained for Sony here https://www.o2.co.uk/business/support/network-support/wifi-and-4g-calling