SOS on my sons 11 iPhone

Review the instructions in this guide published by Apple 👉 If you see No Service, Searching, or SOS on your iPhone or iPad - Apple Support

If you have tried everything listed in the guide, above, then you can:

Contact your carrier 

Issues with your carrier or account might affect your service. Contact your carrier to:

• Verify that your account is active and in good standing.
• Make sure that there are no outages in your area.
• Check that your device isn't blocked from receiving cellular services and is set up with the right data plan.

Only your wireless carrier can access and manage details about your account:

If your carrier confirms that there's no issue with your account or network, but you still can't connect to a cellular network, 👉 contact Apple Support.

Axel F.