You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you at this moment?

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

ASSISTANT: Sure, I am here to help you. Can you please provide your journey dates?

USER: Departure is on May, 30 and return is by June, 1.

ASSISTANT: Do you have any connection limit preference?

USER: I would be comfortable with single stop over.

ASSISTANT: Do you have any other specifications for this trip?

USER: I prefer to fly in a business class.

ASSISTANT: May I know your name to proceed further?

USER: My name is Charles Hill.

ASSISTANT: Charles Hill, there are no flight services available on this route with your preferences.

USER: Thank you.

ASSISTANT: Thank you for contacting us.