Airtel — Internet charges too high

Address:

Bangalore, Karnataka

I called up Airtel customer care to activate internet plan - 99 INR pack which generally gives 1 GB of free usage(2G data) in the last week of billing cycle.
I wasn't informed that the plan is charged pro rata basis.
I didn't get any message regarding the plan activation to my registered mobile number.
I wasn't informed on how much free usage is available and how much i'll be charged for that month on internet activation.
And so i browsed internet and consumed around 600 MB in initial few days.

When i saw the bill, it was 4300 INR. When i asked customer care, they replied that i crossed free usage which is around 200 MB, which is never intimated to me on activation and the rest 400 MB of 2G usage is charged at prorata basis which is around 4k.
Atleast i expect that when i use all free usage, an intimation should be sent to user that additional usage will be charged at prorata basis, which is never the case.

Over all a worst experience with Airtel customer care, and had to terminate mobile services from the provider.