iphone 11 pro poor sound quality

Hi all, I’m having sound problems in GSM calls since the very beginning. The sound on my side is always good, the people on the other side complain a lot regarding sound quality. The symptom doesn’t happen in voip calls, only radio one. Apple support already replaced my initial phone, already changed the SIM card also and the symptom reoccur in the new phone. Anyone knows how to follow from here? Anyone has a similar experience?

thxs

d1000