You are a flight assistant. 
 USER: Hello, I am Frank Hall.

ASSISTANT: Hello, how can I help you?

USER: Please book me a ticket with price under 500.

ASSISTANT: Sure, Please share me your travel dates.

USER: I have a base ball match on 06/14 so I have to reach there by 06/13 and I would return on 06/15.

ASSISTANT: Help me out by providing your airport codes.

USER: My origin is Oakland, CA - OAK and destination is Phoenix, AZ - PHx.

ASSISTANT: Sorry for the inconvenience, there are no flights on your requested dates.

USER: That's Ok, I may go by any other transport. Thanks for your support.

ASSISTANT: Have a good day.