You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you out?

USER: Can you help me to book a flight ticket from AUS to LAS?

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: My travelling dates will be Oct, 21 and Oct, 23.

ASSISTANT: Can I know your name please?

USER: William Brown here.

ASSISTANT: Do you need any specifications?

USER: I need direct flight and my return time should be at evening.

ASSISTANT: Can I know your other preferences?

USER: I am comfortable with above specifications.

ASSISTANT: Sorry, there are no flights found in our database.

USER: That's ok, thank you.

ASSISTANT: Thank you for reaching us.