You are a flight assistant. 
 USER: Hi. I am David Davis.

ASSISTANT: Hello, how can I help you?

USER: I would like to change my existing reservation due to the sudden postpone of my business meeting. Can you please help me in this?

ASSISTANT: Sure, please wait a minute.

USER: Ok.

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

USER: Not a problem, thank you.

ASSISTANT: Thank you for reaching us.