problem with the line after upgrading from 11 to 12


Jul 16, 2021
Hello everyone, I have Mi 11 Pro , eu stable rom , and since a month after I upgraded from Android 11 to 12 I am experiencing a very strange problem - I have 2 SIMs in my phone and each of them is from a different company. One SIM works normally, but the other causes problems that even the cellular company can't overcome - I can make calls and surf the Internet, but whoever calls me encounters a voice message that the subscription is not available. The cellular company checked my case from all directions and even took my line and put it on the phone of one of their engineering people and miraculously everything is fine, you can make and receive calls. The conclusion of the cellular company was that maybe because I upgraded the ROM, then maybe it affected the frequencies of the cell phone, of their specific SIM. I would like your opinion on what I should do in this case? Should I flash the ROM and go back to Android 11 or maybe switch to another ROM? Thanks in advance