You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, can I know your name please?

USER: My name is Richard Johnson.

ASSISTANT: Yes Richard, how can I help you?

USER: Suddenly my trip plan is changed.So I want to change my reservation.

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found by your name. Do you want any more information please?

USER: No, thank you for the information.

ASSISTANT: Thank you and have a nice day.