You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I guide you?

USER: I am Donna Phillips, want to book flight ticket with price under 500. Can you help me with it?

ASSISTANT: Sure, may I know your airport codes please?

USER: Airport codes are ORD-LAS.

ASSISTANT: When would you like to start your journey?

USER: I would like to start my journey on 05/03.

ASSISTANT: May I know your return journey date?

USER: And intend to return on 05/05.

ASSISTANT: Sorry Donna, no flights has been found on your journey dates.

USER: Ok, no issues. Thanks for the help.

ASSISTANT: Thank you for choosing our service.