Samsung Electronics India - Cashback not delivered

I purchased Galaxy tab s*+ from the samsung shop #***********. I had paid using my HDFC credit card and when i entered my HDFC card details at checkout, an instant cashback of **,*** was applied and it was shown on the app that **,*** is the final amount i had to pay. I have also attached a screenshot for the same. The summary shows ***** promotion applied of which **,*** was HDFC cashback. However, the charge that appeared was **,*** and no cashback was received. I raised a complaint for the same, I was asked to share a screenshot of my card statement and was assured that I will get **,*** back from the executive on the call. I did the same. However, they have refused to reverse a charge of **,***. They are saying that i am ineligible for cashback as i had in the previous month used the same card and i got cashback then.
This is a clear case of misrepresentation on part of Samsung. If the card was ineligible for cashback, they should not have shown that cashback of **,*** has been applied when i filled the card details for payment.