You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: I need to buy a plane ticket. Please help me with that.

ASSISTANT: Sure, may I know your connection limit please?

USER: I need a direct flight.

ASSISTANT: Tell me your airport codes please. May I know your name please?

USER: My source airport code is IAD and destination airport code is AUS. I am Paul Anderson.

ASSISTANT: Tell me your travel dates please?

USER: My travel dates are from Nov, 12 to Nov, 14.

ASSISTANT: Do you have any other preferences?

USER: I need to depart in the evening.

ASSISTANT: Please wait.

USER: Ok.

ASSISTANT: Sorry to inform you that presently evening flights are not available.

USER: No problem, thanks for your information.

ASSISTANT: Thank you.