False promise

Location/place: Bangalore

Name of company/service: Sangeetha Mobiles

I purchased a Samsung Galaxy Grand mobe phone from Sangeetha Mobles in FORUM MALL Bangalore on 20/6/2013. They told me that there’s an offer in Vodafone for this mobile and we can browse for 2GB for first 2 months. I didnt receive any message from Vodafone; when contacted they tell me that the offer’s last date was 31/5/2013. How do I proceed? I tried contacting Sangeetha mobiles but they say they can’t help!!!!!