You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how best I can help you today?

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

ASSISTANT: Sure, please share me your trip dates.

USER: Depart is by Oct, 3 and return date is Oct, 5.

ASSISTANT: Do you need direct flight or connecting flight?

USER: I would prefer connecting flight.

ASSISTANT: For booking, we need your good name. Please mention it.

USER: Ruth Moore.

ASSISTANT: Would you let us know if you have any other preferences?

USER: I prefer business class.

ASSISTANT: Sorry to say that, there are no flights available on the routes of your journey.

USER: Thank you.

ASSISTANT: Thank you for choosing us.