You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Steven Green. I am panning to travel from IAD to LAX.Can you help me out to book a ticket?

ASSISTANT: Sure, may I know your preferable dates?

USER: My travelling dates are 05/11 to 05/13.

ASSISTANT: Sure, wait for a minute.

USER: Sure.

ASSISTANT: Sorry Green, no flight's to share the details.

USER: That's fine.

ASSISTANT: Thank you for contacting us.

USER: Welcome.