Call quality issue - iPhone 15 Pro Max

Hello everyone,

I kindly ask advices for a frustrating issue I have with my iPhone 15 Pro max.

Almost every phone call I do with my iPhone sounds interrupted, muffled and unclear, just like when you have a weak signal, but I got a full solid 5G/4G.

I faced this issue with my previous 14 Pro Max also, and always thought the problem is with the person I talk to, but it obviously happens way too often and with too many people.

I traveled between couple of carriers and it happened with each of them, they also claimed there’s nothing wrong in their side when contacted their support in order to check for issues.

I’m running the latest iOS 17.5.1 and there’s absolutely nothing I haven’t tried: changed eSim, reset network settings, reset all settings, factory reset, DFU restore with and without restoring from backup, tweaked some settings, absolutely nothing fixes it!

Did anyone face the same issue and have an idea?

Thank you in advance.