GiftCard object’s statusInquiry() method. If the call shows that the status of the gift card is \Active, you may redeem the gift card.
Determine the status of a Gift Card:
AutoBill and Account objects support redeemGiftCard calls. When redeemGiftCard is successful, the credit granted by the Product (with merchantProductId returned by the gift card processor in response to this call) is added to the Account or AutoBill object against which the call was made.
Redeem a Gift Card, and add credit to an AutoBill:

