Doesn’t Understand The ‘Custom’ Part Of Customer, Part 2

(I answer the phone on a busy day.)
Me: “Hello, [Bookstore]. How may I help you?
Customer: “Hello. Can you tell me if [Competitor] has [Book]?”
Me: “Er… well, I don’t know about [Competitor] but I can tell you that our store has it in stock.”
Customer: “You’re downtown, aren’t you?”
Me: “Yes.”
Customer: “Well that won’t do. I’m not going downtown; I live much closer to [Competitor]. Find out if they have it!”
(If she managed to find our phone number, how hard would it have been to find their number?!)