I read a little. No expert on this. But what I found out: VoLTE is the only way an AW can be used as a phone. No GSM or 3G. So switching this off is almost equal to switching off LTE as a whole. Of course streaming data would still be possible, but the idea of being reachable is gone.
One possible explanation : Apple has changed something on latest models
Or a problem with some series ...
First run this morning and I still have the issue...
I don’t know what to do ...
Sell it quickly as a brand new replacement and get the 6 in a few weeks!