You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How could I provide assistance to you at this moment?

USER: Please book a flight ticket from DCA to AUS?

ASSISTANT: Sure, we are glad to assist you in booking a flight ticket. Can you please let me know your departure and arrival dates?

USER: My journey dates are Dec 11 and Dec 13.

ASSISTANT: Kindly mention your way station in midway of your journey?

USER: I need a connecting flight.

ASSISTANT: Ok, may I know your airline preference please?

USER: I am comfortable with any airline.

ASSISTANT: At what time you would like to begin and return your journey?

USER: I comfortable with any time.

ASSISTANT: Is there any other preferences that you would like to add before?

USER: I prefer a business class.

ASSISTANT: Just wait a moment, I will check the availability of flight and get back to you.

USER: Sure.

ASSISTANT: For further process of booking, can I have your name please?

USER: I am Kenneth Hernandez.

ASSISTANT: Thank you for staying online, we are sorry to inform you that there is no flights are running on your route according to your given information.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for approaching us.