You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation,will you help me?

ASSISTANT: Sure, may I know your name please?

USER: My name is William Jackson.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Thank you for being patience, there is no reservation on your name to change.

USER: OK,not an issue.

ASSISTANT: Thank you for choosing us, have a good day.

USER: Thank you for sharing information.