iPhone shows 'number no longer active' message

I have a message on my iphone that the number is no longer active. It said the SIM had been removed, eSim has been erased or I signed out of a device with my number. It will be automatically removed in 30 minutes.

I did not do any of those things. What should I do? Contact Apple or my AT&T carrier?

[Re-Titled by Moderator]