iPhone 6s Plus: No calls with Airtel SIM

"iPhone 6s Plus: No calls with Airtel SIM: Why my iPhone 6s Plus software version 15.8 is not able to send and receive calls even dialing but it’s just sending and receiving messages only when I’m using Airtel simcard ?"

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In addition to my previous reply.

Troubleshooting Calling:

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

B. "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

C. "No SIM":

"No SIM"*** is shown on the top-left corner of your screen. So, go here to fix that: If you See 'invalid SIM' or 'no SIM' on your iPhone or iPad - Apple Support

D. Install a Cellular Update:

It might be prompting you for a cellular update to install. So, go here for that. Update your carrier settings manually on your iPhone or iPad - Apple Support

E. Whom to Contact:

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

"iPhone 6s Plus: No calls with Airtel SIM: Why my iPhone 6s Plus software version 15.8 is not able to send and receive calls even dialing but it’s just sending and receiving messages only when I’m using Airtel simcard ?"

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Cellular Issues with iPhone 6s Plus:

There is a nation-wide Verizon outage, as of this reply. Some are still having this issue, while others are not. That is the potential culprit here.

Source: Check Network Status - Verizon

As it Reads: "Verizon is aware of an issue impacting wireless voice and data services for some customers. We are working to restore service quickly."