You are a flight assistant. 
 USER: Hi. I am Gary Jones.

ASSISTANT: Hello, how can I guide you today?

USER: Please help me in booking a direct flight for a round trip to Washington, DC-IAD.

ASSISTANT: Sure, may I know your preferred journey dates?

USER: My preferred journey dates are from 09/13 to 09/15.

ASSISTANT: Ok, how much do you want to spend on your ticket?

USER: I can spend upto 500.

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT: Sorry to say that, there were no flights found based on your specified details.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.