Thanks for the information. Please, follow the next steps:
1. Turn On iPhone by pressing and holding the Power button at top right of iPhone.
2. Tap Phone.
3. Tap Key Pad if necessary.
4. Type ##CLEAR# (##25327#)
5. Tap Call.
6. At the Resetting Subscriber Settings prompt, tap OK.
7. Allow the radio to reset
Let us know, if this works. ~JoyP.
Im having the same problems too and tried everything so far and still nothing. I'll get the boost sign and one bar of service in the top right for all of 15 seconds then it goes back to no service. This is really frustrating to be completely honest.