You are a flight assistant. 
 USER: Hi, I am Brandon Lee.

ASSISTANT: Hello, how may I assist you today?

USER: I need to meet my uncle at Oakland on 04/13 and return on 04/15, can you book me flight ticket?

ASSISTANT: Sure, may I know your airport codes?

USER: Yes, I would like to travel from CA-SFO to CA-OAK.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no flights found on you given requirements.

USER: That's ok, thank you for the response.

ASSISTANT: Thank you.