I can’t connect to my carrier

call carrier - I had issue on new iPhone 11 pro and the carrier had to send signals to force my phone to accept the handshake

BUT it worked on wifi calling not cellular

See this...Update your carrier settings on your iPhone or iPad - Apple Support

And/Or...If you see No Service or Searching on your iPhone or iPad - Apple Support

This may apply to your phone...iPhone 7 Repair Program for "No Service" Issues - Apple Support

Also...If you see an Update Failed or Apple Pay Not Available alert after iOS update or restart - Apple Support