My iPhone 7 isn’t working I can’t call and I can’t receive any call

There is no straightforward solution to the issues that you are facing with your iPhone 7 and iOS 13. You cannot go back to the previous iOS version. It is in your best interest if you-

1. Contact your carrier to see whether they can reset your account so that service can be restored on your iPhone 7. If that does not work then-
2. Check to see whether your iPhone 7 qualifies for the ➔ iPhone 7 Repair Program for "No Service" issues - Apple Support.
3. If your iPhone does not qualify for the above then please ➔ Contact Apple for support and service - Apple Support

Axel F.