Airtel — about increased postpaid bill

Sir,

I have a plan of 49 rs per month with 2 gb data per month and 180 minutes in total.
Last month i did not use the total quantity of data and talktime still airtel has charged me extra amount of rupees.

I called them but they told that there are other usage. Means i do not under stand i have not used it for any other purpose still they charged me with extra money.

Airtel wants me to pay a bill of 696.54 rs. Airtel has incurred charges of 576.3 under other usages. But i don't what are the other usage neither they are telling me as i have not used for anyother purpose.
Usage over package is "zero: means i have not used extra data nor extra talktime than why they have charged me more and that too 576.3 rs.

Waiting for my issue to be addressed and solved.