Sam can use credit cards. Because when Sam's member shop pays the bill, it can only be settled after swiping the card to confirm the membership. Otherwise, you will not be able to check out.

Credit card, also called credit card. It is a non-cash transaction payment method and a simple credit service. A credit card is a credit certificate issued by a commercial bank or a credit card company to eligible consumers. Consumers with credit cards can go to specialized commercial service departments for shopping or spending, and then the bank will settle accounts with merchants and cardholders, and cardholders can overdraw within the prescribed limits.