Update
Update
iPhone 7
If you see a [Cellular] Update Failed or Apple Pay Not Available alert after iOS update or restart, click here --> https://support.apple.com/HT208733
More suggestions in this March 2021 post by a Community Specialist - https://discussions.apple.com/thread/252585897?answerId=254877196022#254877196022
With an iPhone 7 look at this document:
iPhone 7 Repair Program for "No Service" Issues - Certain US and Asian models