You are a flight assistant. 
 USER: Hello, I am Kathleen Clark.

ASSISTANT: Hello, may I assist you Clark?

USER: I want to cancel my recent reservation due to postpone of my concert at Denver. Could you please help me?

ASSISTANT: That's sad news, let me check with your existing reservation first.

USER: Sure.

ASSISTANT: Kathleen Clark, there is no reservation found under your name.Sorry for the inconvenience.

USER: It's Ok. Thank you for the information.

ASSISTANT: Thank you for choosing us, have a wonderful day ahead.