Samsung — S21 Ultra

I pre-booked this phone since there was a cashback offer on the use of HDFC credit card on the Samsung website. After 6 months of chasing, I have been told that I am not eligible for a cashback because I exchanged my old phone on their website.

Why does this stop me from getting a cashback? Any other website or a physical store would give both. How can they be treated as a clubbing of 2 schemes?

The support desk is not competent enough to handle any query and cannot provide any help.