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

ASSISTANT: Hello, how can I aid you today?

USER: I am planning to visit the Discovery Green in Houston, TX - HOU. I want to book a ticket from Las Vegas, NV - LAS.

ASSISTANT: Sure, may I know your journey dates and price limit?

USER: My journey dates are 04/19 and 04/21. The price is 500.

ASSISTANT: Please wait a moment I will check the availability of flight and get back to you.

USER: Sure.

ASSISTANT: We are very sorry to inform you that there is no flights available based on your given details.

USER: Ok, no worries.

ASSISTANT: Thank you, have a nice day.

USER: Thank you for your service.