Airtel — charging idle maintenance fee

I have an airtel dth connection. As we know based upon recent trai regulations we need to select a plan and then recharge our account with money. Once the amount is over then we would need to recharge. If the connection is continuous then there is no issue with dth but if we recharge after a gap of 2-3 days then airtel charge idle maintenance fee of 15 rupees. There is no mention of the same anywhere in airtel website or airtel ap. Also if you see the transaction details they do not mention it anywhere. Everytime there is a gap they have deducted 15 rupees from my account. I am not sure what kind of maintenance they are doing on idle account especially when i have paid them money for stb and connection fee when initially i bought the service from them.
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