Vodafone India — overcharged

Address:

110084

I have been charged 9699.26 inr (Unbilled amount) for 2g internet use by vodafone (Prepaid) now my outgoing call has been barded, untill i don't pay the amount. I've never received any notification or warning that i've crossed my credit limit which is 3500 inr. And when asked, they replied that they never wanted to disturb me by the notifications. Is this how it works? Is this right to fool your customers and overcharge them?