You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Kenneth Williams here.

ASSISTANT: In which way can I help you?

USER: Could you help me in changing my existing reservation?

ASSISTANT: Sure, may I know your name for changing reservation?

USER: Kenneth Williams is my name.

ASSISTANT: I am sorry, no reservation found on your name. Thank you for choosing us. Have a nice day.

USER: Ok, you are welcome.