Airtel Prepaid
Wrong deduction of charges for gprs

I have airtel gprs 98 pack which validity ends on 8 march & continue deduction 98 Rs. was charged for next month after midnight for april, i havent stopped pack inbetween i was downloading at midnight i was charged as non 98 pack consumer for 83 Rs. I complaint to 198 costemer servrce what should i do now