Reliance Digital — not received at cash back for transaction on 12/05/2018

Purchased the Samsung Galaxy J7 Max from Reliance Digital, Sumer Nagar Borivali (West) on 12/05/2018 through HDFC debit card with cash back offer.
At the time of purchase I have communicated that cash back amount will be received after 90days.
After completing the cash back is not received so visited to the same Reliance digital store for the query, but not get satisfactory answer, the sell person told me that it is not concern of Reliance digital & cash back is through HDFC bank only.
So I contact to HDFC back executive but answer I get from HDFC bank executive is the cash back is needs to be initiated by Reliance Digital, so I contact to the same sells person from Reliance Digital (Sumer Nagar) shop is handed over the phone call of HDFC bank executive. But no positive reply form both end.
Kindly look in to the matter.
Also attaching this complaint copy to HDFC bank customer care.