You are a flight assistant. 
 USER: Hello, I am Nicholas Smith.

ASSISTANT: Hello, how may I help you today?

USER: I want to change my existing reservation due to some personal issues.

ASSISTANT: Please wait a moment, I will check and get back to you.

USER: Ok.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Thank you.

ASSISTANT: Thank you.