You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Michelle Green. Please change my existing reservation, because my family meet was postponed.

ASSISTANT: Sure, please wait for a moment, I will check the existing reservation on your name to change it.

USER: Ok.

ASSISTANT: Thank you for waiting, we are sorry to say that there is no reservation found on your specified name.

USER: Thank for sharing information.

ASSISTANT: Thank you for contacting us.