You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you at this moment?

USER: I want to do some changes in my existing reservation. Ca you help me for that?

ASSISTANT: Sure, may I know your name?

USER: My name is William Hall.

ASSISTANT: Ok, please wait a moment.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you.