You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Frank Collins from Phoenix. Can you please book a flight ticket from PHX to IAD? As I need to attend a cultural fest in Washington.

ASSISTANT: Sure, when would like to travel?

USER: I need to travel on dates of 07/10 and 07/12.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: You are welcome.