You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what service are you looking for?

USER: I am Melissa Hill, I want to change my reservation due to prepone of my  business meeting. Can you help me?

ASSISTANT: Sure Melissa, please wait for a moment.

USER: Sure.

ASSISTANT: I am sorry to tell you that we didn't find any reservation on your name.

USER: Ok, thanks for informing me.

ASSISTANT: Thank you for checking with us.