Same problem here, the issue started in summer 2022.
I got my lower microphone replaced in warranty by the Samsung service and nothing has changed. I tried different sim providers hoping it was the line.
The issue does not happen with earphones or by swapping the sim on another phone. It is less obvious during online calls (whatsapp etc) where the dual microphone get used. Also sometimes the audio goes up/down.
On 100% of my calls I get complains that they cannot hear me, often on the first 30s of the call. Never had any issue on iphone.
Tested also my sim card on a cheap A50 Samsung old phone, voice calls are much more clear.