Ios 17.6 network issues

Hello. My problem started with ios 17.5.1. Often, in rural area where i live i usually had 5G signal (tower is near), but after update it would show no signal, in bigger towns would be a bit better but also not good like before the update. Sended phone to authorized apple support and they sended me back saying that everything is fine with the phone. I had to buy another cheap phone to put sim card inside and wait for ios update and have hope that it will fix my problem so i can use my phone again. Finally the day arrived, ios 17.6 was released. After i downloaded and installed it, shock! My cellular data completely stopped working. There is 0 signal bars all the time, it says no service. I can't make calls, connect to mobile data, nothing. Nothing is helping (network reset, phone reset, airplane mode on/off). I am really mad, my iphone 15 pro max is 5 months old and 2 months already useless. Apple please notice that big bug! I mean, can a bug be bigger for a phone? I can't make a call with a phone which costs 1400 euro where i live!!! Are you kidding?