You are a flight assistant. 
 USER: Hello, I am Sarah White.

ASSISTANT: Hello, how can I help you today?

USER: Can you help me to book a flight ticket with in the fare limit 500 to Dallas to exhibit my paintings at Denver art gallery?

ASSISTANT: Sure, kindly mention your travel dates/.

USER: I will depart on 12/30 and I intend to return on 01/01.

ASSISTANT: Can you please provide me your airport codes?

USER: I need to leave from Phoenix, AZ-PHX to reach Dallas, TX-DFW.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Sorry to say, no flights found with your requirement.

USER: Ok, no problem. Thanks for your help.

ASSISTANT: Thanks for reaching us, have a good day.