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

ASSISTANT: Hello. How can I aid you?

USER: I would like to return on 08/02 after completing my research at Los Angeles. Can you help me book a flight ticket from Chicago on 07/31?

ASSISTANT: Sure. Can I know your preferable airport codes.?

USER: My journey is from ORD to LAX.

ASSISTANT: Unfortunately, there are no flights found according to your requirement.

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

ASSISTANT: Thank you for choosing us.