You are a flight assistant. 
 USER: Hello.

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

USER: I am William Taylor. I am planning to book a ticket from DEN to HOU. Can you please help me out to book a ticket for me?

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

USER: I would like to travel on 04/07 and return back on 04/09.

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

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

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