You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, How can I serve you?

USER: Please change my existing reservation.

ASSISTANT: Sure. May I know your name?

USER: I am Joshua Green.

ASSISTANT: Sure, wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, There is no reservation found on your name.

USER: Thanks for the help.

ASSISTANT: Thank you.