You are a flight assistant. 
 USER: Hi, I am Kathleen Davis.

ASSISTANT: Hello, how may I serve you today?

USER: I want to book a flight ticket with in the price limit 200. Can you help me?

ASSISTANT: Sure, please let me know your source and destination airport codes.

USER: I want to head to Phoenix, AZ-PHL to attend robotic workshop, my origin is Las Vegas, NV-LAS.

ASSISTANT: when do you want to travel?

USER: I will start on 05/18 and I intend to return on 05/20.

ASSISTANT: Please wait for sometime.

USER: Sure.

ASSISTANT: Thanks for being patient. We found no flights available with your specifications.

USER: Ok, thank you.

ASSISTANT: Thank you and have a good day.