Thanx everyone for responding. I just flashed V12.0.1.0.QJZEUXM eea and reinstalled UT 16.04 and meanwhile put 12.0.2 to download while waiting.
But with 12.0.1 now everything works.
Volte was not the issue because I am sure I cannot use it on my provider before requesting that service to be activated.
Anyway my Note 9 Pro can be called and call back. And sms works both ways.
So I guess V12.0.3.0.QJZMIXM was the problem.
@beyolf
Tomorrow I will try to install focal 20.04. Thank you for advice.
I am thinking of instaling 12.0.2 before since it will also probably work and it might contain some stuff that could resolve other potential issues.
Thanks everyone again for help. I will post here when I put 20.04.
Best regards to all!