You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Jennifer Green. I am planning to visit Washington to meet my father, can you please help me in booking a flight ticket from IAD to SFO?

ASSISTANT: May I know your desired travel dates please?

USER: My travelling dates are July 24 and July 26.

ASSISTANT: Please wait a while.

USER: My departure time is afternoon.

ASSISTANT: Do you have any class preference?

USER: I am comfortable with any class.

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.