You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I am Stephen Edwards. I would like to visit Washington to meet my friend, can you please help me in booking a flight ticket from PHX to IAD?

ASSISTANT: Sure, may I know your travel dates?

USER: My travelling dates are July 25 and July 27.

ASSISTANT: Do you have any specification?

USER: Yes, I need one halt.

ASSISTANT: Sorry, there is no flight on your details.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you.