(I work at the self-checkout registers, helping customers with machine errors and doing theft prevention. Four of our self-checkout registers do not accept cash, to save space.)
Customer: “Where do I insert my cash?”
Cashier: “Sir, this machine accepts debit and credit only. It does not accept cash”.
Customer: “Really? You should have a sign that says that”.
Cashier: “Actually, we have several. There’s one posted just above the register in bright orange, one above the self checkout entrance, and at the beginning of the transaction, you pressed the button that says ‘yes, I understand this machine doesn’t accept cash.'”
(The customers always, with a red face, quickly and quietly run to one of the cash machines!)