Voiding a payment will reverse the payment and make the orders on the payment payable again. So if a customer paid with a credit card but wants to pay with a different card, this is the perfect tool for this scenario.
Navigate to the customers account and then click the "Payment" tab
Click the "Void Payment" button.
3. You will be prompted to add a reason for the refund and pay the amount back to original credit card that was used for the transaction. You can also choose to refund the amount in cash or check.
4. After you submit the refund/void you can now pay the orders that were on the payment with a different payment method or add a coupon to them to fix any error that there may have been. (Note: voiding a payment will bring the orders the payment originally paid for back into an A/R status as "unpaid orders").