You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: Please help me out in booking the ticket from IAH to DCA.

ASSISTANT: Sure, may I know your travel dates?

USER: My trip dates will be Nov 30 to Dec 2.

ASSISTANT: Do you have any specifications?

USER: Return time must be in the afternoon.

ASSISTANT: May I know your name?

USER: Katherine Garcia is my name.

ASSISTANT: Sorry, there is no flight at this moment.

USER: That's ok, thank you.

ASSISTANT: Thank you.