Among other things, the federal Fair Credit Billing Act (FCBA) requires that a credit card issuer promptly credit your payments and correct mistakes on your bill without causing damage to your credit score. It also establishes procedures for settling credit card billing disputes, including those related to unauthorized charges. You must file your dispute within 60 days of when the error first appeared on your statement in order to be entitled to the protections provided by the FCBA. When you dispute a charge, it may result in a “chargeback”—a reversal of the credit card transaction, resulting in a refund to you from your card issuer.
The Federal Trade Commission provides more detailed information about the Fair Credit Billing Act on its website.