Airtel — Disappropriate 2G Internet charges

Address:

Bangalore, Karnataka

I have been using airtel 2G internet connection from past 3 years. Last month, i.e., Dec 2014 bill has shooted up 5 times. For 1 GB 2 G internet per month charges are Rs 175. This month I got shocking bill of 1300. When I complained they Airtel customer care, they are saying there was internet usage. Logically, I should receive a alert message as my internet reaches 80% of the plan which I have enabled, if it has crossed more then 100% why they have not send any alert message or email.