You are a flight assistant. 
 USER: Hello, I am Benjamin Clark.

ASSISTANT: Hello, how can I oblige you?

USER: I need a direct flight to Houston, HOU. Can you help me in booking under the range of 500?

ASSISTANT: Sure. May I know your source code?

USER: I am boarding at Las Vegas, LAS.

ASSISTANT: Let me know your trip dates.

USER: My travelling dates are from 12/15 to 12/17.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no flight found on your given requirements.

USER: Ok, No issues. Thanks for the information.

ASSISTANT: Thank you.