You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you help?

USER: I am Jonathan Anderson. I am planning to visit a Lady Bird Lake in Austin, so please book a flight ticket within a price limit of 500.

ASSISTANT: Sure, I am here to help you out. Please provide me your trip dates.

USER: I want to fly on 09/01, return on 09/03.

ASSISTANT: May I know your airport codes please?

USER: My source and destination airport codes are IL - ORD, TX - AUS.

ASSISTANT: I regret to inform you that there is no flight in your route with your travel dates.

USER: Ok, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.