I use Authorize.net, and at least once a week a customer emails (before shipment) to add items to their order. I don't know where, or if, I can find their CC # to charge them for the added items. Up till now, I have just told them they need to go back to the website, order the item, and I send them a coupon, or process a refund for the additional shipping they pay through the website. It would seem a simpler thing to just be able to charge their CC for the item itself - without the requirement that they re-login, purchase, etc...

Any suggestions?