Activating Cellular on Apple Watch 5

Hello,

I have been trying to enable cellular on my Apple Watch 5. I have a iPhone 12 Pro with iOS 14.3 and Apple watch 5 with OS 7.2

Everytime I try to activate cellular the watch app on the phone says "Unable to Configure Cellular Plan".

Tried restarting both the watch and phone multiple times but the message persists.

Is it a problem with the Network (Airtel in India) or a bug on either the phone or watch?

Can someone help.

Thanks.