Can't add credit card to my account

I tried purchasing some Call of Duty coins last night on my Xbox account, and my purchase kept being declined. I tried again on the MS Store app on my PC and it was declined. I was trying to use the same CC that I have had on my account and have never had a problem before. I deleted the CC and now when I try to add it back as a payment option I keep getting "Check the info you entered. It doesn't match the info for this card." I know that the info I'm putting in is correct. I called customer support and they are saying that this card has exceeded the number of accounts that it can be associated with. I don't understand this, I only have one account and this just started happening last night when I've never had a problem before.

:)