You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am looking for a flight from IAD to SEA, can you please help me in booking?

ASSISTANT: May I know your desired travel dates please?

USER: My travelling dates are Feb 25 and Feb 27.

ASSISTANT: Do you have any specifications?

USER: I prefer business class.

ASSISTANT: May I know your name please?

USER: My name is Brian Taylor.

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

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for opting us.