Airtel — charging my main account while I'm using internet service

Address:

Angul, Odisha, 759122

Sir i'm using your 399 pack for 84 days @ 1gb per day. But today exactly at 2:40 pm when i'm using my internet a message came saying your last data use 0.56 mb and charging 5.36 rupees from your main account, but i'm using internet pack which is still active and also my today internet balance is more than 600 mb for today, so how can they charge my main mobile balance.
So i want my money back and guarantee this will not happen in future