iMessage activation unsuccessful

Imessage has been refusing to activate my phone numbers (Telekom Slovenija +386 .....) for more than a week. The phone has been updated before. Telekom Slovenije informed Apple about the error, but the company did not respond and did not correct the error.

Even a network reset and a complete phone reset does not help. I am very disappointed with the Apple iphone 12 promax pro, as it does not work Imasege, facetime.