Unable to make or receive calls on Airtel sim

Most likely, your phone is not compatible with the AT&T network.

That phone is definitely not compatible. It wouldn’t even be allowed on the network with an ATT SIM card. 

I am surprised how come data is working and only incoming and outgoing are not working 

It’s because ATT does not support that phone for ATT’s version of VoLTE. Without that, calls don’t work.

Ok thanks 

Hello viinshan21, we're here to give you answer about service on your Xiaomi 11 Lite NE.

Let's thank both Aces for responding. No Xiaomi phones have been certified by AT&T to use on their network. If you purchased an unlocked device from another retailer, please note, they are not optimized to work on AT&T’s network. This is important to remember when purchasing a non-branded, unlocked device and why you see different model numbers. You'll find a full list of compatible devices. 

Please reach back out if you have any other questions or concerns.

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Carlton, AT&T Community Specialist