You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, may I know your name please?

USER: I just want to change my recent reservation because my business trip postponed. can you help me for that?

ASSISTANT: Sure, please provide me your name?

USER: I am Margaret Hall.

ASSISTANT: Are you sure, that you have booked with this name?

USER: Yes.

ASSISTANT: Then sorry, there is no reservation.

USER: It's ok.

ASSISTANT: Do you want any more information please?

USER: No thanks.

ASSISTANT: Thank you and have a nice day.

USER: Welcome.