- Completely turn off your iPhone.
- Insert the SIM eject tool or a short paperclip into the designated slot on the SIM card tray with your phone turned off to unlock it. On the right edge of your phone, you'll find the SIM tray.
- The SIM card should be removed from the SIM card tray. Look for any apparent evidence of damage on the SIM card. If everything appears to be in order, replace the SIM card in the SIM card tray.
- Place the SIM card in this position: the gold contacts facing down.
- Insert the SIM card tray.
- Press in on the tray to lock it into place.
When the SIM card tray is locked in place and secured, turn on your iPhone and see if the No service error is gone.