The first post doesn't tell us the source of the charges. My assumption is that this is a case of identity theft. In which case the name on the card is incidental.

If it is identity theft, I am surprised that credit card company is suing. Credit Card companies are extremely irresponsible when they send out mass mailings for pre-approved cards.

Now, if Charley was the person who made the charges, then Charley is liable for the charges, even if the name on the card was the nickname and not the legal name.

A $5800 credit card bill doesn't just appear from the aether. If Charley was buying things with the card and signing receipts without the intention of paying the bill, then Charley was fraudulently entering a contract with the merchant. Singing legal documents with one's nickname is not an out from the contract.

Many of the Williams, Josephs and Edwins of the world sign Bill, Joe or Ed.

The major question in this case is the identity theft and not the wrong name on the card. The wrong name simply adds to the identity case plea.