Cellular Update Failed - iphone 7

Hi

Phone works fine on WIFI, but cellular connection is not working. Carrier Verizon says it's an Apple issue with iphone 7. Things that work for very short time but then drops again - sim card out of phone and put back in, turning phone off and back on (soft reboot and hard reboot), re-setting Network settings.

Any other ideas?

How do I get permanent help?

Thanks so much!