Call failure issue on iPhone 13 after software update

"I have iPhone 13 which is facing the problem of call failure after software update. For which I even reset all the settings but still the timing is not resolved, what should I do for this?"

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Troubleshooting Calling After an Update:

A. "No Service":

Is "No Service" shown on the top-left corner of your screen? If so, go here to fix that: If you See No Service or Searching on your iPhone or iPad - Apple Support

B. Calls: If you can't Make or Receive Calls on your iPhone - Apple Support

C. Whom to Contact:

Contact your Carrier, as they are the one who provide you with the service of Calling.

D. Report this to Apple:

Do your Part: Provide Apple with feedback on this, letting them know about this issue.  Apple may not get back to you directly, but the more feedback they receive on this, the more they will know what is occurring, and what bug fixes to include in updates to come. Apple will know nothing of you occurrences, if you don't report it to them.

1. Go Here: Feedback - iPhone - Apple
2. Select: "Bug Report" for the "Feedback Type"
3. Comment: that this all began after installing an update. Include the URL of this thread
4. Proceed from there as necessary