You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello. How may I serve you?

USER: Could you please book a ticket from Las Vegas, NV-LAS to Oakland, CA-OAK.

ASSISTANT: Sure. May I know your travelling dates?

USER: My travelling dates are from 05/19 to 05/21.

ASSISTANT: Do you have any preferences?

USER: Price limit is 500. I need direct flight.

ASSISTANT: Please wait. Thanks for waiting. There is no direct flight available to your destination. May I know your good name?

USER: My name is Sarah Nelson. Thanks.

ASSISTANT: Thank you.