Why my airtel extreme recharge charges 706 Rs. for 499 plan?

So i got the airtel extreme installed in my home with 3 months recharge
My parents delayed the payment by 25 days until the service stopped one day.
then we recharged so it asked for 700 hundred rupees for 499 plan as delayed payment charge(maybe)
but after that we payed on time
still it asks for 700 rs everytime we rahcharge for 499 plan. Can anybody tell me what is wrong??