You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I be a help for you?

USER: I want to change my reservation, becasue I have another important work on those dates so I am unable to catch the flight. Can you please change my reservation?

ASSISTANT: Sure, may I know your good name please?

USER: Sure, my name is Robert Campbell.

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

USER: Oh! It's ok no problem. Thank you for your information.

ASSISTANT: Thank you for approaching us.

USER: Welcome.