Did you do what they said, contact your card issuers customer service department, if so what did they say?
Yes and for some banks, you gotta contact them before purchasing/adding your debit card in order to use them online.
Do you have any other bank's debit card such as hdfc,icici,axis etc. ? Have you tried adding them as well ? DON.
I added my HDFC international debit card today with success. You have HDFC international debit card or normal debit card?