Greetings! Welcome.
Physical sim card:
turn off phone > take out sim > lightly rub the brass colored contacts with a pencil eraser (not your finger. & don't leave eraser residue) > put sim back in
Are you on WiFi with airplane mode on? Or WiFi at all? This may not be working right.
settings > system > reset options > reset mobile network
Contact cell carrier describing your issue and actions taken to remedy and if the actions changed anything afterwards.