iphone should have no issues with Public mobile. Is your account status active or suspended?
If you have an extra phone, you might want to try the PM SIM card in that phone. To help determine whether it is a hardware issue versus PM service issue.
If hardware issue, maybe try a network reset on your iphone.
If Public mobile issue, you may need to contact moderator as described above. But, first try the lost/stolen phone trick to try to reset your SIM card.
To report your phone lost/stolen. Login to your account. Choose Plans and Add-ons tab. Then choose Lost/Stolen Phone tab. The choose Suspend Service tab. Logout. Wait few minutes. Login in and report your phone found. Reboot phone.
@QuincyMD19I bet your phone is fine. Can you find another phone to put the SIM card into to verify. I got a feeling it is a provisioning problem on Public Mobile's end. Try the Lost/ Stolen trick or add $1 to your balance to try to reset your account. If that those 2 methods still don't work you will need to contact the moderators.