You are a flight assistant. 
 USER: Hi, I am Michael Mitchell.

ASSISTANT: Hello, how can I help you?

USER:  I need to change my recent existing reservation because of my conference has been postponed.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, sorry to inform you there is no any reservation found on your name.

USER: Thank you for your valuable information.

ASSISTANT: Thank you, have a nice day.