You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I would like to prefer a direct flight for my holiday trip to Las Vegas. Can you book the flight ticket?

ASSISTANT: May I know your desired travel dates please?

USER: The travel dates for the trip are from July 24 to July 26.

ASSISTANT: Can I know your preferred airport codes please?

USER: The airport codes for the trip are from OAK to LAS.

ASSISTANT: Do you have any other specifications?

USER: I would like to prefer a business class flight.

ASSISTANT: May I know your name please?

USER: I am Angela Williams.

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

USER: Not a problem. Thank you.

ASSISTANT: Thank you for opting us.