how to fix cellular issue

See -> If you can't make or receive calls on your iPhone

If you can't make or receive calls on your iPhone - Apple Support

Hey,

I had this issue as well after the latest update. Do you use an eSIM?

After contacting my carrier, they had me try it with the physical SIM instead—if you don't have one, order one from your carrier. Try it with a physical SIM. Though Apple had said it was a hardware issue, my carrier concluded it was the eSIM (embedded SIM) in the phone that had broken. Unfortunately, I must keep it on the physical SIM, but this solution restored service to me and helped me avoid a pricey repair.