Airtel — Airtel deducting money unethically

I was very surprised to know that Airtel DTH is charging Rs. 15/- on every delayed recharge, and they have been charging this every month.
My DTH was valid till 12th Jan, 2022 midnight, and I recharged the full amount on 13th Jan 3PM. However, to my surprise, I saw Rs 15 has been deducted. On going through the laborious process of talking to a customer care exec, I found out that this is due to 'Late Fee'. Now, I don't understand, how is this late fee. A person will take their bike to the service center only after it breaks down, right and not before that. So, even if I recharge the immediate next day, they are charging this amount. To top it off, there is no prior communication regarding this amount. It's kind of happening in stealth, so they are cheating unsuspecting people of Rs 15 everytime. This is a loophole they are using to perform corporate fraud.
Please beware of this.