If I can't pay for my purchases, why can't Apple get rid of the fine?

I spent $22 in the Apple Store on a couple apps and songs with a credit card, but recently I found out that the card didn't go through even though there was money on it. I just want to understand why I can't return my purchases. I can't download any free apps or any of my past apps that I already downloaded because it keeps telling me that the verfication is required. I've tried to enter the credit card information all over again but it still says the card didn't go through.