Airtel — No network in my phone poor service from Airtel

Address:

Airtel

Sir,
I am have been using airtel sim from 9 years. All of sudden i lost my network from my sim overnight and did not receive any support from customer service. On sending them the email, they ask to authenticate the number with email using the otp sent to my number.
How is it possible to receive the otp if there is no network in my sim. They dont provide any customer service either. All my bank account is linked to this number. And in times like this i am facing such problem. Is this how they treat their customer who has been using their services for so long.
I am very urgent need getting the network can they pls look into the matter?