Dell India — Cashback not received

I purchased a new laptop from dell (https://www.dell.com/en-in) using hdfc credit card on 1st feb 2020. There was an offer of 10% cashback upto ₹8000 on purchase of dell 5590 laptop using hdfc credit card. The cashback was supposed to be processed within 90 days from the date of purchase, however, the cashback is still not processed even after 5 months! I have complained them but they have given me false promises multiple times and keeps delaying.
Order number is[protected]