You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, How may I assist you today?

USER: I am Kenneth Campbell.

ASSISTANT: Ok.

USER: I want to change my existing reservation , please help me out.

ASSISTANT: Sure. Please wait for a while, I revert to you.

USER: Ok.

ASSISTANT: Thanks for your time, but no reservation is found on your name.

USER: That's fine, thank you.

ASSISTANT: Thank you.