@Yukontrevor Other things to try, update ios if update available, restart phone, take sim card out and reinsert (if possible try it in another phone then put it back), update carrier settings, turn off any VPN. Those are suggstions from Apple forums. There's also this from Apple
https://support.apple.com/en-us/119837
If none of that works contact Apple support. It seems that it is something that can happen with iPhones. Apple may say check with carrier which you can do by opening a ticket at the chat icon bottom right of this page but it seems to be more of an iPhone issue. The hotspot on my iPhone works fine and I never had to contact Public Mobile to set it up.
