[Resolved]  Airtel — company threatening to stop my sim card despite having balance in account

I'm an Airtel customer since a decade, using the same number for ten years. I'm using this number as my primary communication and personal number. Linked to office/work and many other services. The account is active. But Airtel is threatening to Stop my service if I don't recharge with ₹35 regularly. This is wrong and unfair practice.
My account is active and there's activity in the sim. But threatening to recharge regularly, is unfair and it is upto me if I want to recharge or not. At the time of registration, I was told this was life time validity.
How come this is allowed by TRAI? I don't think TRAI set any regulation regarding this.
Please take an action on Airtel or they will lose a long and loyal customer.
My contact number is : +91 [protected]