No you will not get the 5% cashback. Rather buy a Amazon Gift card from Amazon from millennia card and add that gift card in your amazon account and make the payment. You will get 5% cash point in your credit card which you can redeem later in which 1 cashpoint is equal to Re 1
Using HDFC Millenia Credit Card on Amazon Pay for Mobile recharge will give you Flat 5% cashback in statement.
But while going to pay UTILITY bill payment, Amazon Pay will charge 1.18% (including GST) Platform fee & also give 5% cashback.
Cashpoint redemption fee is 50 Rs. + 18% GST.