My iPhone 12 Pro updated to iOS 14.4 and now my phone has no longer cellular connection. I put the SIM card on my old iPhone 6 and it works perfectly, so the problem is not my carrier. I called Apple support and they were useless, just told me basic things like “turn your phone off and on again”. In fact, the representative hadn’t even heard about this issue with iOS 14.4 (when there are dozens of people with the same problem just on this thread). I totally regret not turning off the auto installation option! It’s irresponsible of Apple to put out software that hasn’t been fully tested, I really hope they fix it soon.