You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello,. How can I help you?

USER: My name is William Jackson. I want to change my existing reservation.

ASSISTANT: OK, Please wait for a moment.

USER: OK.

ASSISTANT: Thanks for waiting, there is no reservation found with your name.

USER: OK, Thank you for your service.

ASSISTANT: Thank you, Have a great day.