when i go to purchase a song or app it tells me my card is declined but i know i have money on that card

Your card is registered to exactly the same name and address as on your iTunes account (and you are currently in that country) ? If it is and you've checked with your card issuer to see if it's them that are declining the card, then you culd 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 Purchases, Billing & Redemption