Myntra.com — false advertisement of cashback on citi credit card

Website:

Myntra

Mymta offer for cashback of 10% on citi credit card on purchase of rs 3000 above but on doing same didn't get cashback, contacted customer care, they say the offer is for specific card starting with some number selected by mantra, who will write this in term and condition, falsely making offer and on call saying there was some other condition as well. I fulfilled all condition as stated in their app but how am i suppose to know that offer is valid for specific citi card. I am highly unsatisfied with their false advertisement of offer.