You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: John Parker here.

ASSISTANT: Ok.

USER: Please help me out in booking the flight ticket from LAS to PHX.

ASSISTANT: Sure, can I know your preferable dates?

USER: My trip dates will be 12/13 to 12/15.

ASSISTANT: I am sorry, there are no flights available. Thank you, have a good day.

USER: That's ok, anyways thank you.