Hi there. iPhone XR running latest iOS. Cellular data is turned on, and sending over web works fine with iMessage, but I cannot receive or send regular text messages nor can I send or receive phone calls. Flummoxed. It's been like this half the day.
Are you by any chance connected to WiFi? If so, iMessage will work just fine. I think the issue here is that you are either not getting any cell connection or your account may not be fully activated. When did this start and has it ever worked?