If you are unable to make a call or receive; If you can't make or receive calls on your iPhone - Apple Support
Cellular Update Failed —> If you see an Update Failed or Apple Pay Not Available alert after an iOS update or restart
Settings > Mobile Data > APN [under Mobile Data APN] enter the APN pin
View and edit your APN settings
If your carrier allows it, you can view your APN settings in one of the following locations: Settings > Cellular > Cellular Data Options > Cellular Network. Settings> Mobile Data > Mobile Data Options > Mobile Data Network.
View and edit your Access Point Name (APN) on your iPhone ...
Carrier Update (Required): Released by your Cellular Service provider (Carrier Update), affects your Outgoing / Incoming calls, SMS, Data etc.
How to Update Carrier Settings
You can manually check for and install carrier settings, and update with these steps: Make sure your device is connected to a Wi-Fi or cellular network. Tap Settings > General > About. If an update is available, you'll see an option to update your carrier settings.
Update your carrier settings on your iPhone or iPad - Apple Support
If nothing helps then --> If you see a Cellular, Ultra Wideband, or Apple Pay Issue message after an iOS update or restart
