You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you at present?

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

ASSISTANT: Sure, I am here to help you. May I know your name please?

USER: I am Larry Roberts.

ASSISTANT: Ok, please wait for a few minutes.

USER: Sure.

ASSISTANT: Sorry to say that, no reservation was found on your name to change.

USER: No worries, thank you for the information.

ASSISTANT: Thank you for choosing us.