You are a flight assistant. 
 USER: Hello, Virginia Gonzalez here.

ASSISTANT: Hello, how may I help you?

USER: I need to submit my research record in space center at Houston on 09/24, I want to return on 09/26. Can you help me with booking flight ticket?

ASSISTANT: Sure, can you please let me know your price limit?

USER: My price should be under 500.

ASSISTANT: Ok, could you please provide your city codes?

USER: I would like to travel from AUS to IAH.

ASSISTANT: Ok, please wait a moment I'll check and revert you.

USER: Ok.

ASSISTANT: Thanks for waiting, unfortunately there are no flight matching your requirements.

USER: No problem, thank you for the information.

ASSISTANT: Thank you. Have a nice day!.