Same problem here. Updated to iOS 14.2, no service for 2 days already!... Nothing helps. At first I thought I got into some IMEI block issue, but the operator said everything should be fine. Strangely enough, the phone continues to work with one of the three operators I could get a SIM card of.

I think the problem is observable with specific operators only, have you guys tried SIM cards from different carriers?

iPhone 11 Pro, tried updating to iOS 14.3 public beta - did not help, the problem is still here.

I was considering to bring my iPhone for a service check - and actually called 2 certified Apple service providers, but they didn't seem to be aware of the problem... So I became hesitant to get left without my main work phone for like what... 2 weeks? I now get the problem partially solved by switching to another operator (whose SIM card somehow appears to work). P.S. I created a Facebook group, named "iOS 14 no service support group" to gather all the people that got affected by the problem - feel free to join. Maybe together we will find a decision different from switching to Android. :)