Phone only works with Wi-Fi

[Malcolm_1678400]

I can no longer receive or accept calls on the mobile network, but I can make and receive them when on Wi-Fi.  Why is this?  I have not changed any settings on my phone, I have checked everything (data is on, do not disturb off, I’ve updated my phone, I’ve taken the SIM out and reinserted it, I’ve switched the phone off and on etc etc) but still it does not work over the network.  My next step appears to be to change provider.  Can anyone advise why this is?  I must be able to make and accept calls when away from Wi-Fi.

[SmartyTrousers]

This is most likely because your phone is not compatible with Smarty's VoLTE (4G calling). Previously, phones which are incompatible with Smarty's VoLTE will have been switching down to 3G to make or receive calls, but most of Smarty's 3G coverage has now been turned off.

See this page for more info (note that the list of incompatible devices there does not appear to be comprehensive).