Wrongly Billed/False Promise by vodafone

Location/place: Guntur

Name of company/service: Samsung/Vodafone

I have bought a Samsung Grand Mobile on 21 st April 2013 and have been promised 2 months of 3G data of 2GB by Vodafone.
I have a Vodafone sim and have used the service. But now I have got a Post Paid bill of 6600 and most of it was for Data Usage(2G/3G). When I called customer care they told they don’t have such offer.
Please look into this.

My MailId is [email protected]
and my vodafone number is 9959222926