If bill amount is higher like 20k or more, then Hdfc sends you consent message only after clicking on the link & submitting the otp, you get Billpay scheduled message.
Check that message if that's the case....see below ss of sms I got.
u need not to wait until this long closer to due date.. it normally schedules within a week after bill generation..if not we shud move to pay differently and delete/add the CC again in smartpay to see atleast for next month..