You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I serve you?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure. May I know your name please?

USER: I am William Robinson.

ASSISTANT: Wait for a moment please. Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you.