You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, firstly may I know your name please?

USER: I am Brian Davis.

ASSISTANT: Davis, how can I assist you now?

USER: I want to change my existing reservation as my plan to visit Museum of  fine arts got rescheduled.

ASSISTANT: Ok, please wait for a while.

USER: Ok.

ASSISTANT: Sorry Davis, there is no reservation found on your name.

USER: That's fine, thank you for the information.

ASSISTANT: Thank you for approaching us, have a nice day.