https://www.desidime.com/discussions/credit-card-75-k-ayment-max-benefit-for-hdfc-preferred-platinum-debit-card-which-gives-1-on-all-transactions?page=1#post_8739653
HDFC bill pay portal will give 750 on using platinum debit card for credit card payment. Go to bill pay in netbanking, add credit card for payment. While paying make sure you select platinum card in the drop down, pay with it.