Prompt credit for payment
A card issuer must credit your account on the day the issuer receives your payment, unless the payment is not made according to the creditor's requirements.

Refunds of credit balances
When you return merchandise or pay more than you owe, you have the option of keeping the credit balance on your account or receiving a refund.

Unauthorized charges
Most credit card companies have programs like the Visa Zero Liability policy, where cardholders are protected from unauthorized transactions made on their cards, provided that they can establish, to the satisfaction of their bank, that they didn't make the purchase.