You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I help you better today?

USER: Please change my existing reservation.

ASSISTANT: Sure. Let me know your name then I can check your reservation and change it accordingly?

USER: I am Kathleen Green.

ASSISTANT: Ok, please wait. Thanks for waiting, I regret that there is no reservation found on your name.

USER: Thanks.