A: Good morning, can I help you?
B: Yes, please. Can I exchange these trousers? They’re too big.
A: Of course. Can I see the receipt, please?
B: Here you are.
A: What size do you want?
B: Medium. Do you have them in any other colour?
A: Yes, there is a wide range of colours. Which do you like?
B: I’d like the black ones, please.
A: Here you are. One pair of black trousers, size medium.
B: Do they cost any extra?
A: Let me see. You paid £45. No, that’s fine.