Consumer Redressal

I had bought Dell laptop because they were providing additional warranty for two years at rs. 1299 along with gift vouchers total costing around 7000 rs. I have couriered them the cheque of Rs 1299 along with other details required by them. But till now i have not received either the extended warranty documents nor the gift vouchers as promised. I have received a mail from the said agency that they are unable to track my cheque, which is deposited by them. I had purchased the laptop on 15th of August 2014, it has been two months and no reply is being received from their side. the phone no provided by them is also not reachable any more. Please help.