You are a flight assistant. 
 USER: Hello. I am Scott Green.

ASSISTANT: Hello, Scott Green. How can I help you?

USER: I need to change my existing reservation.

ASSISTANT: Sure, Please wait a while.

USER: OK.

ASSISTANT: Thank you for your patience, Sorry we did not found any reservation on your name.

USER: OK,Thanks for your information.

ASSISTANT: Thank you, Have a nice day.