I brought songs using te Itunes store now it is saying invalid payment method now for some reason?

I have been buying music from Itunes for months now, but suddenly it is not letting me pay for music. I know my password and username is correct, my billing information is also correct. But everytime I try to confirm payment it repeats the same message. "Your payment card was declined. Please provide valid payment card information." Can someone point me in the right direction? Thank you.