The customer made a claim of an "incorrect electronic funds transfer" as defined in 1005.11(a)(ii). They authorized one amount and was charged another amount. Since the customer made a claim, you have an obligation to provide provisional credit if you cannot resolve the claim in 10 business days from the date of initial notice. Under Visa/Mastercard rules this would not be eligible for a fraud related chargeback since the customer has a relationship with the merchant.
Other potential chargeback options may be "Incorrect Amount" or "Merchandise Not Received" if the cardholder claims that they were charged too much or did not receive merchandise for the charges they claim are improper.