Vodafone India — Overbilling on postpaid connection

Address:	Mumbai City, Maharashtra
Website:	www.vodafone.in/home-mumbai

I have been using vodafone postpaid connection with monthly rental of 375(corporate sim) which has 1Gb free internet.
I had received alerts via email as well as message in phone that I will be charged at 50p/Mb on extra internet usage but they have charged wrongly at around Rs4/Mb.
This has happened since August. On regularly taking and emailing I got a revert for the month of December only.
I made payment for Dec once it was corrected. But they now issued a bill which includes charges for Dec also.
And for Jan they have shown 650 against MI_CAP_650_30d_R_PROMO_3G, which says after extra internet billing of 650Rs no charges will be taken.
But my charges for extra internet havent exceeded this limit.
Another concern is that the 1Gb free data is not given, instead only I got 932 Mb and they charged again at 4Rs/Mb after that.
Hence i got a very huge bill amount. And on top of that 14.5% total tax also.
I have mailed then again and made the payment of rest of the amount.