You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

USER: Can you help me to book a flight ticket from DFW to PHX?

ASSISTANT: May I know your travelling dates?

USER: May, 23 and May, 25 are my travelling dates.

ASSISTANT: Can I know your connection limit?

USER: I would prefer single connection.

ASSISTANT: Please let me know your name?

USER: Margaret Smith here.

ASSISTANT: Do you have any other preference?

USER: I need to depart at evening time.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Sorry, no flights available on your route.

USER: That's ok, not a problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.