Wrong country code for incoming calls in roaming...

Hello, on my iPhone 13 Pro, I have a constant problem with incoming calls when I am in roaming. For some reason, the phone automatically adds the country prefix of the country where I am roaming instead of the real caller country prefix. I have tried enabling and disabling Dial Assist, but nothing changed. I have also contacted my provider and I was informed they had numerous reports that iPhone users have the same problem, and they have checked- the problem is not on their side... I have also tried SIM card from a different provider, and the same problem occurs.

What should I do, since Apple doesn't have Official Support in my Country?