You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: I want to change my existing reservation due to postpone of my exams.

ASSISTANT: Sure, I am here to help you with that changing reservation. Can I know your name please to proceed for further?

USER: Myself Kenneth Harris.

ASSISTANT: Please wait for a moment, let me check your previous reservation status.

USER: Ok.

ASSISTANT: Thank you for waiting, but I am sorry to tell you that, there is no reservation found on your name in our database to change it.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Most welcome, thank you for contacting us.