HDFC Bank — Cashback did not received after 5 months

I purchased an iphone 11 dated 12/02/2020 having an offer of 6000 cashback. Even after 4months, i have not received my cashback. Bill copy is attached for your reference.

Card no.[protected].
Ph. No [protected]

Note - i have visited one of your branch and they told me to visit store from where you buy phone and when i visit store they told me talk to customer care and then customer care told me to visit branch. Why un-necessary harassment.
Even in lockdown you are offering cashback offer online then why not return our earned cashback. It is already been 5 month.
Please do the needful.