⟩ Suppose the credit card machine is broken. What do you say to the customers?
I’m sorry for the inconvenience, but we are still able to take cash or checks. There is an ATM nearby, so if you would like to get cash, I would be more than happy to hold your merchandise for you.
I would offer to hold the customer’s merchandise for up to 48 hours and call them when the machine is working again. Then, they could retrieve their merchandise and pay with a credit card.