HI Thank you for contacting Apple Support, i understand that's frustrating
as your phone is unable to connect or locate your network
If you see No Service or Searching
If you see No Service or Searching on your device, or can't connect to a cellular network or cellular data, follow these steps:
Check your coverage area to make sure you're in an area with cellular network coverage.
If you can't connect to a cellular network, make sure cellular data is on in Settings > Cellular.
If you're traveling internationally, make sure your device is set up for data roaming. Go to Settings > Cellular > Data Roaming.
I See you have already contact your carrier, removed sim & reset settings, check your phone no is correct by checking
settings-> phone
enable location services
check date & time settings, settings>general> date & time
if none of this works last resort would be to restore to factory settings