4g shows but no internet access

I have an iPhone XS Max on 15.2. I used this with the Vectone network. Everything was fine. About a month ago I went to Italy and the SIM card wouldn’t work even with the settings that Vectone told me to change. I came back and discovered I no longer have cellular internet access. Wifi, Bluetooth, calls and texts all work perfectly. I have switched carriers and the issue is still present. The carrier is stumped and said go to apple. I have tried near enough every trick in the book: resetting network settings, updating apn settings, restarting etc. if I factory reset and restore, it would just restore the phone to the same configuration of no internet access with data right? What are my other options?