You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Could you please book a flight ticket from Dallas & Fort Worth to Phoenix?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: May I know your class preference?

USER: I don't have class preference.

ASSISTANT: When are you willing to travel?

USER: I am willing to start on 12 Feb and intend to return on 14 of Feb.

ASSISTANT: Are you flexible to depart and return any time?

USER: Yes, I am flexible to travel at any time.

ASSISTANT: May I know your airport codes?

USER: My airport codes are DFW to PHX.

ASSISTANT: Please share your name to proceed further.

USER: Sure, my name is Jerry Moore.

ASSISTANT: Sorry to inform you that we didn't find any flight on given dates.

USER:         That's fine, thank you for the response.

ASSISTANT: Thank you.