HDFC Bank — hdfc credit card - iphone 11 cashback not received

I bought an iphone 11 dated 8-feb-2020 in pune apple store, as per the transaction receipt from hdfc my transaction is eligible for 6000 cashback within 120 days, i haven't received the cashback yet and my the complaints to the help desk via email and the relationship manager are of no use. I hope this issue will be addressed in this forum and the cashback is credited as soon as possible.