A:Answer Technically, the new phones are VoLTE or Voice over LTE capable and 3G is only needed if LTE is down.
This phone also have 5G but currently, 5G has no Voice call and it goes thru the LTE.
3G is only needed for the older Phones without VoLTE or for back up but LTE is becoming obsolete now because of the 5G.
most of the Freq. are on this phone ,just double check the Freq bands on this phone and AT&T.