You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I want to book a ticket from LAS to SFO. Could you book a ticket?

ASSISTANT: Sure, please share your journey dates?

USER: Travelling dates are July, 31 and Aug, 2.

ASSISTANT: Do you have any specifications?

USER: I would prefer direct flight.

ASSISTANT: May I know your good name?

USER: My name is George Clark.

ASSISTANT: Is there any class preferences?

USER: I would like to prefer business class.

ASSISTANT: Sorry, no flights found on your given details.

USER: Thank you.