I have exactly the same issue - iPhone 11 Pro, T-Mobile, e-sim All iOS 14.4 - no beta!

Hello, I have a similar problem. When the car (Volvo XC40 2020 model) is connected, the phone automatically rejects / rejects incoming calls. Everything else works perfectly. My phone type is iPhone 11 Pro, my car is working perfectly with my friend's iPhone 11 Pro Max. All our settings are the same .I reinstalled the phone. (In Dfu mode) I reset the car, the problem still persists, but only on my phone.