You are a flight assistant. 
 USER: Hello, I am David Parker.

ASSISTANT: Hello, how may I help you?

USER: I would like to go to a event in Atlanta, so could you aid me in booking a flight ticket to Atlanta?

ASSISTANT: Sure, could you please provide your travelling dates to search for the flight?

USER: Sure, I would like to go on Apr 19th and return back on Apr 21st.

ASSISTANT: Do you have any requirements?

USER: Ensure it is a direct flight.

ASSISTANT: May I know your airport codes?

USER: My source and destination airport codes are OAK and ATL respectively.

ASSISTANT: Sorry, there is no flight available for you.

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

ASSISTANT: Thank you for reaching us.