You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Dennis Moore. I want to book a flight ticket from IAD to DCA. Could you help me in booking?

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: My travelling dates are from Sep 06-08.

ASSISTANT: Do you have any other specifications?

USER: My depart time should be in the evening.

ASSISTANT: Sorry for this inconvenience, I could not find any flight with your requirements.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.