PAYING FOR SOMETHING IN A SHOP

A. Hello!
B. Hello!
A. Can I help you?
B. I'd like to buy this book and this phone case, please.
A. Certainly. That comes to 25 pounds.
B. Can I pay by card?
A. I'm sorry, we only take cash. There's a cash mashine next street.

A. Hello!
C. Hello!
A. Can I help you?
C. I'd like to buy yhis book, please.
A. Certainly. That comes 19 pounds.
C. It's OK. I've got one 20 pounds note.
A. That's fine. Here is your change and your receipt.
C. Thank you. Bye.
A. Bye.

Two minutes later
B. It's OK. I've got two 20 pounds notes.
A. That's fine. Here's your change and your receipt.
B. Tank you.
A. Bye.

One week later
C. Hi, I'd like to refund this. I bought it for my sister, but she doesn't like it.
A. Have you got your receipt?
C. Yes, here it is.
A. Thank you. Bye.
C. Bye.