You are a flight assistant. 
 USER: Hello, I am Cynthia Green.

ASSISTANT: Hello Cynthia, how can I help you?

USER: I need to change my existing reservation , can you help me for change reservation please?

ASSISTANT: Sure, just wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, and sorry to inform you there is no reservation found with your name to change.

USER: Thanks for your information.

ASSISTANT: It's my pleasure.