Offer your thoughts or opinion on the input financial query or topic using your financial background.

Does a failed chargeback affect my credit score?
I think your confusion comes from the negative impact when a creditor writes off your bad credit and ceases attempting to collect it. "Chargebacks" as you call them are an attempt to undo fraudulent charges on your card, whether from stolen credit card info or from a merchant who is using shady business practices. For what it's worth, if you joined on December 20, January 20 seems like a reasonable date for the next billing cycle, with the December 31 date reflecting the fact that their system couldn't automatically bill you the day you joined. I also think it's reasonable for you to ask them to refund the bill for the second month if you do not plan to use their gym further. So the dispute seems like a reasonable one on both sides. Good luck.