I had a problem a long time ago where my phone was saying no service and that’s because of the recall they had on this model of the phone. It is doing the same thing and I cannot use the phone.
iPhone 7, iOS 13
This info might not help because you seem to indicate you had your phone fixed or replaced but review it anyway and if it does not help you need to contact support.
Update your carrier settings on your iPhone or iPad - Apple Support
If you see No Service or Searching on your iPhone or iPad - Apple Support
iPhone 7 Repair Program for "No Service" Issues - Apple Support
This info might not help because you seem to indicate you had your phone fixed or replaced but review it anyway and if it does not help you need to contact support.
Update your carrier settings on your iPhone or iPad - Apple Support
If you see No Service or Searching on your iPhone or iPad - Apple Support
iPhone 7 Repair Program for "No Service" Issues - Apple Support
Why does my iPhone 7 keep saying no service
