You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: Can you please book a flight ticket from ATL to DCA?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: May I know your travel dates please?

USER: Sure, I have planned my travel dates as Sept 02 and Sept 04.

ASSISTANT: Ok, do you have any specifications?

USER: I would like to return in evening time only so please make sure that.

ASSISTANT: May I know your name please?

USER: Sure, myself Nancy Brown.

ASSISTANT: Sorry Nancy Brown, there are no flights available on your requested dates.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.

USER: Most welcome.