You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: My appointment with my manager has postponed, so I would like to changing my existing reservation, will you help me with this?

ASSISTANT: Sure, I am glad to help you. Can I know your name please?

USER: My previous reservation has been done with the name of Richard Miller.

ASSISTANT: Miller, no reservation found with your name to change further.

USER: Ok, not an issue. May be something went wrong while booking the ticket.

ASSISTANT: Ok.

USER: Thank you for providing information.

ASSISTANT: Thank you.