Phone saying no service

Did you already try theses troubleshooting tips?

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If you get an alert that says Invalid SIM or No SIM Card installed, follow these steps.

1. Make sure that you have an active plan with your wireless carrier. 
2. Restart your iPhone or iPad.
3. Check for a carrier settings update. Go to Settings > General > About. If an update is available, you'll see a prompt to select OK or Update.
4. Remove your iPhone SIM card or iPad SIM card from the SIM card tray and then put the SIM card back. Make sure that the SIM tray closes completely and isn’t loose. If you use a SIM tray from a different model iPhone, iPad, or from another phone manufacturer, it might not fit properly.
5. Try using another SIM card. If you don't have one, go to your carrier's retail store and ask them to test with another SIM card. You might need to replace your SIM card.

If you still see an alert about your SIM card, contact Apple support.

Learn what to do if you see a SIM not supported alert.

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copied from: If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support

Restoring the phone to factory settings and setting it up again with the SIM card inserted would be the next step, before you contact Apple Support.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Click on the blue link above and follow the steps mentioned.

In case this does not bring your cellular network back, contact the Apple Support:

Contact Apple for support and service - Apple Support

Did you also try another SIM?

If restoring did not work, the next step would be contacting Apple Support or visit an Authorized Apple Support Provider and let them diagnose your device:

Apple - Find Locations