Payment method declined

It's not a pre-paid card, the card is registered to exactly the same name and address (including format and spacing etc) that you have on your iTunes account, and it was issued by a bank in the country where you can your iTunes account are ? If it is then you could check with the card issuer to see if it's them that are declining it, and if not then try contacting iTunes Support and see if they know why it's being declined : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Account Management