You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I assist you?

USER: I need to change an existing reservation.

ASSISTANT: Sure, May I know your good name?

USER: My name is Justin Brown.

ASSISTANT: OK, Please wait for some time.

USER: Sure.

ASSISTANT: Thank you for waiting, We did not find an existing reservation on your name.

USER: OK,Thanks for your information.