HDFC Bank — Tv/consumer durable loan cashback complaint

I had purchased a sony tv using hdfc cashback offer on 29/10/2019
The offer stated that within 90 days (3 months) the cashback will be credited in the bank account but yet i have not received the cashback and hdfc helpline are not working and is of no use at all.
This was purchased from Croma Koramangala, we were in a follow up with hdfc sales executive in 3rd month, he said that it will be coming in 5th month loan completed on 6th of aug 2020 till now we have not received cash back amount 3884 no response from manager also.

Kindly look into the issue and credit my cashback into my account at earliest.
Looking forward for your early reply.

My hdfc consumer durable loan no -7271116
[protected]@gmail.com
Reg mob no-[protected]