[Resolved]  HDFC Bank — cashback promised not received

I bought samsung galaxy s9 on 5/10/18. There was a scheme going on purchase of samsung handsets if purchased via hdfc credit card or consumer durable loan. You get 5000rs instant cashback and rs6000 cash within 3 months/90days. I was informed this by the hdfc representative at the store who showed me offer information. I myself checked about it and found it is true as i am attaching of same offer which continued in dec also. I have already paid 3 installments and it has 97 days but i have still not recieved cashback of rs.6000.
I contacted hdfc consumer durable helpline but waiting for average 15 min multiple times no one picked call. Kindly help in this issue as i feel cheated by the hdfc bank.