Connectivity issue iPhone XR - can’t make a call

Hi

I have a problem where my iPhone XR recognizes a SIM card and shows full connectivity bars, but these blank out when I try to make a call and I effectively can't make or receive calls. I rebooted, tried different SIMs, etc.

Similar things happen on WIFI, where even though the device is connected to WIFI, it failed to allow me to log into iCloud in main settings, saying it’s not connected to the internet.

This smells to me like a hardware replacement issue? Could someone point me to the right resource which exact part to replace

I have experience in fixing Macs, but none in iPhone repair

Any advice appreciated