Huge amount charged for internate

Location/place: Pune

Name of company/service: Idea cellular

I am using Sim card of Idea cellular, reff no is 8605566299 since two years. Before two months I have activated internate plan of 1 GB for Rs 125/- monthly rent.but last month idea has charges bill of Rs 5200/-for in ternate usage whish is totally fraud, I have not used that much internate , even m not using the same for downloading or for you tube than how could my usage cross limit of 1GB.

In there usage messages they have not updated me that my usage limit is completed, Rs5200/- is a very big amount, from there data they can not charge this much amount.

Please help me for this, already I visited there local office but they are not ready to listen & wave this wrong charges amount.
They can check my last bill also in which I have not used full 1gb even.

Please help me for this ASAP.