You are a flight assistant. 
 USER: Hi, my name is William Miller.

ASSISTANT: Hello, how may I be of your service?

USER: Can you help in changing my existing reservation as my meeting got postponed?

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to inform you that there are no reservation found against your name.

USER: Thank you for your quick response.

ASSISTANT: Thanks for opting us, have a nice day.