You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: I am Timothy Carter. I would like to book a flight ticket within the fare limit 500 to Settle, can you help me to book an economy class ticket?

ASSISTANT: Sure, can you share your trip dates?

USER: I intend to start on Jan 20th and my return date will be on Jan 22nd.

ASSISTANT: May I know your airport codes for booking?

USER: My source and destination airport codes are JFK and SEA.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT: Sorry, there is no flight available at your request.

USER: No issues, I'll choose any alternative to reach my destination. Thank you.

ASSISTANT: Thank you for opting us.