You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am William Clark. I want to book a flight ticket from DFW to PHX. Could you help me in booking?

ASSISTANT: Ok, may I know your travelling dates?

USER: My travelling dates are from Dec 22-24.

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT: Sorry, no flights found on your route to reserve your ticket.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.