You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am planning to book a ticket to attend a meeting at HOU. Can you please help me out from LAS?

ASSISTANT: Sure, can you please help me with your travel dates?

USER: I am planning to travel on Dec 21 and return back on Dec 23.

ASSISTANT: May I know your name?

USER: Sure, I am Williams Miller.

ASSISTANT: Do you have any requirements?

USER: No.

ASSISTANT: Sorry, there is no flight available as per your requirements.

USER: That's fine, thank you for your service.

ASSISTANT: You are welcome and thank you for choosing us.