Need help apple itunes won't accept my billing information when everything is right and correct

What type pf payment info are yout trying to add to your account and what happens when you do so ?

If it's a debit card then I don't think that they are still accepted as a valid payment method - they are not listed on this page and there have been a number of posts recently about them being declined

If it's a credit card 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 if 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 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

If it's a different problem ... ?