Re: Not that simple - some 4G/5G devices and/or SIMs currently use 3G and 2G for voice!
>you'd expect that all 4G handsets would work.
But then I'd be out of a job ;-)
Unfortunately there are a lot of settings that need to match in the network and the handset for VoLTE to work. Originally only operator custom software had those, and only for the network they were designed for - take that handset to another network and you're back to 3G/2G voice.
The GSMA spotted the problem and built a settings database; since 2019 most handsets will automatically install the right config for the SIM they are given. Of course there were a lot of handsets sold between 2015 and 2019, and many of them are still in use....
Biting the hand that feeds IT
