false bill

Filed on: 24/08/2014 | Loss amount: Rs. 1300.0
Dear sir I m using tata Docomo post paid sim from last two months on 9501765616. And using gsm bang plan of 222 rs and 1 gb data for 125 rs per month .from last two bill they were billing me correctly.but now bill for this month they wrogly billed me.I m using data pack only on what’s app and face book they showing that I hav used 500 mb approx in one day after my data pake over 1 gb.on 21aug afternoon they send me one message that your billing amount is 860 rs and near to my monthly limit of 1200 rs per month now they send me bill of 1336 rs.my billing cycle is from 20 july to 19 aug then how can they add my aug month of data in july month bill….they never intimate that how much data I hav used and how much left .and I hav not downloaded a single audio song as well then how can I use 500 mb data in one month….now when I m calling to Customer care they are not telling me that where I have used that much of data.plz help me sir and plz see my data till the time my one gb pack was not over it was approx 30 mb per day but as soon as my data over past one gb they show that I have used 500 mb per day how can it is possible….plz help me out sir from this wrongly bill.