No servis

Is this a new problem on an existing account on your carrier--if so contact the carrier for assistance.

Otherwise, see the tips in the link if you know your phone should work on the network you are trying to use.

If you see No Service or Searching on your iPhone or iPad - Apple Support

The only other reason the OP would see that and I'm taking a wild stab in the dark, is that the phone is blacklisted. Or, he could try one of the suggestions you put forth.

(Edited to add the words "he could try" to make it clearer)