Flipkart — Cashback not credited in my Bank Account

I purchased a mobile phone for Rs.26, 499 on October 11-2018, with order ID OD[protected], and it was delivered on October 15-2018, through my debit card. There should be a cashback refund of Rs.2000. But it is still not reflected in my account. I have contacted Flipkart customer care multiple times, and they were saying that the refund was done processing from their side on November 8-2018. And they have given a transaction reference number as 5392029215276860304055. Its been more than four years, and I am yet to get a resolution for this.