You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: Myself Carolyn Anderson. I want book a ticket from LAS to PHL.

ASSISTANT: Sure, can I know your preferable dates?

USER: My preferable dates are from 11/19 to 11/21.

ASSISTANT: I am sorry, there are no flights available.

USER: Thank you.

ASSISTANT: Thank you, have a good day.