If your ex is a co-borrower, demand the credit card company close the account, and inform them you will no longer be responsible for charges made on that account. Of course, the credit card company in turn may demand payment in full of the account.
If your ex was only a person you granted permission to use the account, then inform the credit card company that permission to use the card is revoked. And this still may not settle the issue. Best bet: pay it off and close it. Then you can enjoy the satisfaction in your mind of your ex going to charge something and being informed the account is closed.
Answered on Aug 15th, 2012 at 2:50 PM