Turn Airplane Mode on, wait 10 seconds, then turn it off
Restart your phone
Check your cellular signal and move to a different location if needed
Make sure your SIM card is inserted properly
Remove and reinsert the SIM card
Check for a carrier outage
Make sure Cellular Data is turned on
Turn off and on Mobile Data or Cellular Data
Update your carrier settings
Update your phone software
Reset network settings
Check that your account is active and in good standing
Contact your carrier
Contact emergency services only if you are in danger or need help