Cellular issues
Why is my mobile data not working for internet or calls
iPhone 12 Pro Max, iOS 16
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See these Apple articles below:
If you see No Service, Searching, or SOS on your iPhone or iPad
If you see No Service, Searching, or SOS on your iPhone or iPad - Apple Support
Manually update your carrier settings on your iPhone or iPad
Manually update your carrier settings on your iPhone or iPad - Apple Support
Update your network provider settings manually on your iPhone or iPad
Update your network provider settings manually on your iPhone or iPad – Apple Support (UK)
If you can't make or receive calls on your iPhone
If you can't make or receive calls on your iPhone - Apple Support
Contact also your carrier and check your data plan.