When Emily complained of poor call quality I tried enabling Wi-Fi calling on her 13mini -- and got this error message:
We've hit a bump, but we should have it straightened ... ERR0093-WS
Don't worry, it will never get straightened. This is a crap error message. A pixel page gave me the answer.
Chances are you SIM-Swapped this phone to avoid an infuriating $50 activation fee from AT&T. Turns out that only seems to work, the IMEI in AT&T's system doesn't update. If your plan has HD Voice (most do) it's not working and Wi-Fi (WiFi) calling won't work.
We called AT&T new line support (chat was down) at 611 and after a bit of careful navigating got a human being in "advanced technical support" who updated the IMEI number for us. You may also be asked for the ICCID number. After a phone restart and waiting a few minutes Wi-Fi calling worked. Her voice quality also seemed better.
I did this for a different phone and the first agent said I needed a new SIM -- then (accidentally I think) dropped me. A second agent wanted IMEI and ICCID then told me to restart the phone. It seems to take 3 minutes or so for the change to propagate and enable Wi-Fi calling (and HD Voice by the way).
If you SIM swap to avoid AT&T's #$@$ $50 activation fee you should probably call support or take your phone to an AT&T store to fix the IMEI there.
What's the chance AT&T will ever give up on its activation fee grift? Would be nice for them to just do an eSIM without the fee.