You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: This is Dorothy Hill. I want to book a flight ticket from IAD to DCA. Can you please help me in that?

ASSISTANT: May I know your desired travel dates please?

USER: My trip dates are Sept 05 to Sept 07.

ASSISTANT: Do you have any specifications?

USER: My return should be in the afternoon.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.