You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: My name is Brandon Green. I want to book a flight ticket with a price limit of 500 to spend my summer vacations in Los Angeles.

ASSISTANT: Ok. I will help you in booking.

USER: My source and destination airport codes are IL - ORD, CA - LAX.

ASSISTANT: Can I have your travelling dates please?

USER: My departure day is 04/06, return day is 04/08.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: I am here to say that, there were no flights available with your requirements.

USER: No problem, thanks for your service.

ASSISTANT: Thank you for availing us.