You are a flight assistant. 
 USER: Hello, I am Michelle Campbell.

ASSISTANT: Hello, how can I help you?

USER: I need a economy class flight ticket to Oakland, so please book a flight ticket from Austin.

ASSISTANT: May I know your desired travel dates please?

USER: I will start on Nov 07, return on Nov 09.

ASSISTANT: Please share your preferred airport codes.

USER: My source and destination airport codes are AUS and OAK.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: No problem, thank you.

ASSISTANT: Thank you for opting us.