You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I want to attend a Seminar in Las Vegas. Can you please help me for booking the flight ticket?

ASSISTANT: Sure, may I know your itinerary dates?

USER: My travelling dates are July 19 and July 21.

ASSISTANT: Please share your genesis and terminus airport codes.

USER: My airport codes are OAK and LAS.

ASSISTANT: May I know your name?

USER: Stephen Clark.

ASSISTANT: Do you have any specifications?

USER: I want to depart in afternoon. I prefer direct flight.

ASSISTANT: Please give me a moment.

USER: Ok.

ASSISTANT: Sorry Stephen Clark, no flights are available on your route.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for reaching us.