You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you?

USER: I need a direct flight to Denver, CO - DEN. Can you please help me in booking a flight ticket?

ASSISTANT: Sure. When are you planning to go?

USER: I am planning to go on 09/15.

ASSISTANT: Ok. Where are you heading from?

USER: Washington, DC - IAD is my origin.

ASSISTANT: May I have your name? Thanks for sharing your details.

USER: Richard Collins is my name.

ASSISTANT: Ok. Unfortunately, no flights are available on respective dates. Thank you.

USER: Can you please check once, return date is on 09/17.

ASSISTANT: I have checked, but sorry to say no flights.

USER: Ok, thanks for your service.