You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, do you need any help from us?

USER: I am Ryan Williams. I am planning to book a ticket from DCA to DEN. Can you please help me out?

ASSISTANT: Sure, could you please share your departure and arrival day?

USER: I would like to travel on 05/05 and return back on 05/07.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

USER: That's fine. Thank you for your service.

ASSISTANT: Thank you for approaching us, have a great day.