You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. In what way can I be at your service today?

USER: There is a football match in Denver between Boston and Denver team, so I want to book a ticket, can you help me?

ASSISTANT: Sure, I can help you with that. Can you please help me with the exact airport codes of Denver and your nearest airport code?

USER: My departure airport is Boston-BOS and in Denver the airport is DEN.

ASSISTANT: Ok, on which date you are going to travel?

USER: Departure from Boston is on 06/13.

ASSISTANT: Ok, do you want a return ticket too?

USER: Yes, I want to return from Denver to Boston on 06/15.

ASSISTANT: Ok wait a while, I will be back with the best service for you. Can I have your name please?

USER: Sure, my name is Robert Smith.

ASSISTANT: Robert, sorry to say that there is no flight available on your route.

USER: That's ok, I will check for other alternative. Anyway, thanks for your service.

ASSISTANT: You are welcome. Thank you for reaching us, have a nice day.