return from recall causes duplicate cc charge

There is a problem I have seen when using F11 recall for return from a transaction paid with credit card. Use F12 for the payment screen and the amount is populated on the same tender line, then press enter on that line and the expiration date and approval code is already populated. Swipe the card, and the card is charged again instead of returned, then the balance (twice that amount) is returned to the default tender (in our case cash). Our EDC method is PCCharge through Paymentech if that matters. Our solution has been to instruct the cashiers to delete the approval code before swiping the card, but when that isn't followed the customer gets double charged. Does anyone have a better solution?