What can you do about a credit card dispute if you have an additional card and your sister used her card in 2003 for 6K and now they are having a problem paying it off and you are having problems also?

If I understand correctly, your sister is a co-signer on an additional card also held by you, and both of you are having problems re-paying the debt. If this is the situation and the charge you are trying to dispute is the 6K from 2003, there's nothing you can do. If she was not a co-signer, then you will have to file criminal charges which I would assume you wouldn't want to do. Overall, the best advice for someone in over their head with financial strain is to try to refinance with any equity you may own in personal property, or see financial counseling to consolidate your debt. If you are behind in your payments, the credit card company may work with you on the remaining balance. Good luck