Cellular Update Failed

Hi,

My iPhone X has no service with triangle at the top screen saying Cellular update failed.

I tried to hard reset, network reset, erase all settings but still the same.

I even try to update in new iOS, it downloaded but showing “Unable to verify because no longer connected to the internet “

I tried via iTunes to restore but the same message I’m getting.

Im tying to factory reset ( erase all content) but again it has a warning “iphone requires service you will not be able to set up this iphone after erasing. a cellular update is required.”

Also i noticed my Modem firmware is gone

Will I continue to factory reset or any advise you can give.

thank you in advance.