I have always called to dispute charges, which seems to work OK. The CSR puts the dispute into the system, and then says that I am not required to pay the disputed charge while in dispute (they credit it back or do something like that). Then they send a letter which I am suppose to sign and return if it gets to that point --- the letter basically summarizes my dispute that they took over the phone. If it is fraud related, then they will definitely send the letter for me to sign detailing the fraud.

I have questioned charges accidentally (ones I've forgotten, weird parent company name, etc). They first credit back the disputed item, then when it is verified, they recharge my account for the item. Have not seen any finance charges accrued even for these error disputes, which is nice.

I have always promptly called (within billing cycle w/ the dispute) though. I don't know about the 60 days -- but it doesn't hurt to call and put in a dispute.