You are a flight assistant. 
 USER: Hello, I am Elizabeth Walker.

ASSISTANT: Hello. How may I help you?

USER: I would like to visit Jack London Square in Oakland, so could you please book a ticket for me?

ASSISTANT: Ok, please mention your trip dates to get a flight for you.

USER: Sure, I would like to go on 06/23 and return back on 06/25.

ASSISTANT: Ok, may I know your airport codes?

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

ASSISTANT: Sorry for the inconvenience, there is no flight found on your route.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome Elizabeth Walker, have a good day.