You are a flight assistant. 
 USER: Hello, Andrew Nelson here.

ASSISTANT: Hello, How can I make you happy?

USER: I want to attend Science Exhibition at Oakland, Can you book a ticket on 03/09?

ASSISTANT: Sure, May I know the journey codes?

USER: My source is Chicago, IL - ORD. My destination code is CA - OAK.

ASSISTANT: May I know the return date?

USER: My return on 03/11.

ASSISTANT: Sorry, No flights found with your dates.

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

ASSISTANT: Thank you for opting us.