You can cancel a card that has not been printed yet. Once your card has been canceled, a card credit will be added to your account and will automatically be applied to your next order. See "How do card credits work?" Note: If this was an automatically generated card, you will not be charged for any canceled cards and no card credits will be added to your account. See "How can I cancel an auto-send card?"
To cancel a card, sign in to your account and go to your "Scheduled & sent cards" (http://www.cardgnome.com/timeline). Find the card that you would like to cancel, and click on the "Cancel card" button underneath the image of the card.