My cell phone provider is Ting. They started sending me emails last May that by January 2021 they would only provide 5G and if your phone doesn’t have 5G then u would need a phone the provided VoLTE (Voice over LTE). They also said that my current Sony Xperia XZ does not provide VoLTE. I searched around and did find a couple people posting that the XZ does have VoLTE but they were not in America like me. I decided it was a software issue if the hardware is in my phone and that perhaps Sony had just not enabled that feature in American software.
I had put many different ROMs on my previous phones and had /e/ working before on a Moto G4. I liked the OS and since then have had Google issues that made me want to de-Google like /e/ offers. Unfortunately /e/ doesn’t have software for the Sony Xperia XZ and I went with a ROM called crDroid 5.12 that is based on LineageOS.
I put that on my phone back in October till now in February and my voice calls are fine. There were a lot more mobile network types to choose from. VoLTE is not in there and I searched what these names mean and it seems like these are all pre 5G networks.
Here are 3 screenshots on the XZ showing which mobile networks are offered:



There’s also a test I ran that says VoLTE is now provisioned
There are Sony phone codes that may work on the XA2 as well. Dial this in the phone app:
* # * # 4636 # * # *
select Phone Information
This is a screenshot that I see on the XZ

I have had some problems with this ROM on my XZ, though. My front selfie camera doesn’t work. My rear video camera does not work (still shots do work out the back of the phone).
I’m thinking that since the XA2 is 2 years newer than the XZ that it has better hardware and VoLTE can be similarly activated with LineageOS and it seems like I’ll have my video camera to use again!
Marty