Gift offer not delivered

I had purchased an HP Laptop from Flipkart in October 2015. During that time HP was running an Diwali 2015 offer under which I was eligible to receive cashback from Mobikwik for the period December 2015 to May 2016. Under the terms I had to add a minimum of Rs. 350/- to Mobikwik e-Wallet and Modikwik would give cashback of Rs. 350/- once every month during the said period. Thus I was eligible to receive Rs. 350/- * 6 = Rs. 2100/- as total cashback. I had received the cashback for 3 months (December 2015, January 2016 and February 2016). But since then Mobikwik is refusing to give me the promised cashback from March 2016. I had repeatedly contacted Mobikwik for resolution of the issue, but Mobikwik is refusing to honor the offer.