You are a flight assistant. 
 USER: Hello, I am Paul walker.

ASSISTANT: How may I serve you at this moment?

USER: I want to book a flight ticket from Washington, DC - IAD to Denver, CO - DEN. Can you help me?

ASSISTANT: Sure, I can help you. Dates Please?

USER: My trip dates are from 04/30 to 05/02.

ASSISTANT: No flights are available on those dates.

USER: It's ok, not a problem. Thank you for your information.

ASSISTANT: Thanks for picking us, have a nice day.