Consumer Redressal

I had purchased a Samsung Laptop on 15.06.2013 attracted by the advertisement by Samsung offering Tablet at a discount of Rs.7000/- But they have not given me the discount coupon stating that the invoice given by the dealer did not mention the serial number of the product purchased. After several enquiries they have given me the discount voucher which is valid only for less than 6 hours on 20.09.2013. They have deliberately done this to deny me the offer.