Once I was using a different access point, for which they charge 10p/10kb (2G days) instead of the one I should be using to avail the 2gb/Rs98 plan - and I got a bill of around Rs2000. I called them and said that I'm not going to pay as I was not aware of the two different access points and no one from Airtel clarified me. Well, though I didn't expected, the removed the whole data usage amount my bill.
You're one Luckiest Guy. They usually RIP OFF the customer be it Mobile (prepaid,Postpaid) /DTH/Broadband/ 3G/4G. Worst Mobile Player soon to be thrashed by Idea cellular.