You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I help you today?

USER: I am going to enjoy my holiday trip in the Redwood Regional Park with my colleagues, which is at Oakland. Can you book me flight ticket with price under 500?

ASSISTANT: May I know your journey dates?

USER: I want to travel on 04/28, and need to catch return flight on 04/30.

ASSISTANT: Can you please help me with your airport codes?

USER: I need to leave from my nearest airport SEA to reach OAK.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: May I know your good name please?

USER: I am Donald Thompson.

ASSISTANT: Sorry, there is no flights found on your given details.

USER: Ok, no problem. Thanks for the information.