i am trying to change credit card to settle a balance and it wont accept the new card

What happens when you try to add it ? If it's a credit card (I don't think that debit cards are still accepted) then is it registered to exactly the same name and address (including format and spacing etc) that you have on your iTunes account, it was issued by a bank in your country and you are currently in that country ? If it is and it's being declined 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 can help : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Account Management