iTunes wont accept my credit card info. Help!!

Ok. I have and iPhone and ive had it for a while with no problems. I recently closed the back account that my iTunes account was linked to.. So i went in and changed my account information in itunes to my new debit card. I thought everything was good until i tried to download and app from the app store. It told me to check my purchase history in iTunes to resolve the problem. So i went into purchase history to find out I owe $1.06 from an app i bought a couple of days ago. I checked my credit card info and its all correct.. when i click Done the page refreshes and it says. "Please enter valid security code".... ive done it a hundred times and im puting in the correct info. What can I do to fix this???