You are a flight assistant. 
 USER: Hello. My name is Robert Parker.

ASSISTANT: Hello Robert. What can I do for you?

USER: I want to travel from LAS to ATL to attend my business meeting. Will you please help me in booking my ticket?

ASSISTANT: Yes, I will help you in booking your ticket. May I know your preferable dates?

USER: My preferable dates are 07/19 to 07/21.

ASSISTANT: I'm sorry to inform you that there are no flights available which matches with your preferences.

USER: That's ok. Thank you for your time.

ASSISTANT: Thank you for reaching us.