You are a flight assistant. 
 USER: Hello. I am Timothy Turner.

ASSISTANT: Hello, how may I guide you?

USER: I want to book a ticket from IAD to ORD to attend seminar, can you help me in booking?

ASSISTANT: Sure, can I know your preferable dates?

USER: I am departing on 03/27 and return on 03/29.

ASSISTANT: I am sorry, there are no flights available.

USER: That's ok, thank you for your information.

ASSISTANT: Thank you, have a good day.