You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Jeffrey Moore.

ASSISTANT: Jeffrey Moore, how may I assist you today?

USER: Can you book a flight ticket from AUS to DEN?

ASSISTANT: Sure, I will help you. Please help me with your planned travel dates.

USER: My preferable travel dates are Apr, 21 and Apr, 23.

ASSISTANT: Do you need a direct or connecting flight?

USER: I need a direct flight.

ASSISTANT: Please let me know with your preferred departure and arrival time.

USER: My depart time should be at evening.

ASSISTANT: Jeffrey Moore, I am really sorry that there are no active flights available as per your preference.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us. Have a great day.