Redmi — offer cashback not credited even after a year

Address:

Ghaziabad, Uttar Pradesh

I had purchased redmi 4a mobile from flipcart for rs 6999.00 on october 5, 2017 through my axis bank debit card. As per the orevailing offer, 10 percent of the price had to be credited back in my account. But it is not done yet though almost an year has passed.
The invoice number of the purchase was :
Pl: f24538996. Was the offer a sham? Please make the flipcart honour it's commitment.