VoLTE stopped working on iPhone 8/iPhoneSE

[uasw]

Slightly more than a month ago VoLTE and native WiFi-calling suddenly stopped working for all the services linked to my account. When making a voice call, the network falls back to 3G. Optus’ 4G network is greatly superior, so on many occasions you’ve got 4G coverage and no 3G coverage at all.

My handset is iPhone 8 Plus, all VoLTE settings are in place (iOS 11.3, Enable 4G -> Voice and Data, and Wi-Fi calling -> on, General -> About -< Service provider OPTUS 32.0). I tried resetting settings and restarting phone many times, no luck at all. On my wife handset, iPhone SE, which is linked to the same account, VoLTE stopped working at the same time.

Any ideas what may be wrong?

[SamSam · Accepted solution]

Sounds like for whatever reason Optus' backend system deactivated your VoLTE access (which is also tied to WiFi calling). I'd jump onto live chat and ask them to take a look - http://yesopt.us/chat2us

[uasw]

All right, there was a problem on the backend, just as yo suggested. Had a very quick chat - and VoLte is back now, Very happy