You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, I am happy to help you. Can you please let me know your travelling dates?

USER: Departure is by May, 21 and return date is May, 23.

ASSISTANT: Do you prefer any stopover in between journey?

USER: I would prefer direct flight.

ASSISTANT: Are there any other specifications for you?

USER: I prefer business class.

ASSISTANT: Can I have your good name?

USER: My name is Anthony Hill.

ASSISTANT: Sorry, no flights are available on your journey routes.

USER: Thank you.

ASSISTANT: Thank you for contacting us.