HDFC Bank — iphone 11 cash back still haven't received

It’s been 6 months since i have purchased my iphone 11 from an authorised apple store in select city walk, new delhi. It’s a disgrace for me to even come to the extent of complaining this matter but it is highly not what would expect from hdfc bank. I haven’t received the cashback that i was promised while buying the phone from my hdfc card.