a card payment system includes a purchases assistance system linking online merchants of goods or services , including digital goods , with the operator of the card issuance system . merchants can use the purchases assistance system to seek help from the issuer for resolving disputes related to purchases of digital goods of which the provisioning may have failed , to trade better commercial terms from the issuer in exchange for providing details of products purchased by cardholders , to verify the balance of debit cards and request a reservation of funds from the issuer to lower their financial risks prior to certain types of transactions , or to signal to the issuer special loyalty rewards associated with specific purchases .