(Whenever a customer asks for cash-back, I always repeat the amount back to them just to make sure I have heard correctly.)

Customer: “Can I have £30?”

Me: “That’s £30?”

Customer: “No, £30.”

Me: “Yes, £30 cash-back?”

Customer: “No, I want £30.”

Me: “Yes, that’s what I said, £30 cash-back.

Customer: “Look, do you do cash-back?”

Me: “Yes.”

Customer: “Well, can I have £30?”