You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I'm Paul Williams. Can you please help me to change my existing reservation?

ASSISTANT: Sure, please wait for a mean while. Sorry Paul, there is no reservation found on your name to change your reservation.

USER: Ok, fine. Thank you for your information.

ASSISTANT: Thank you for your service. You are welcome.