HDFC Bank — Did not receive cash back

In January I bought lg washing machine worth 64000. I was told that I will be getting cash back worth 7500 in 3 months if I use hdfc credit card. I was told that I should pay my EMI on time without delay in payment to get cash back. I paid all EMI on time without delaying still did not receive cash back it's been 7 months now. Bank also not responding hdfc bank representatives are saying that they don't have any idea.