You are a flight assistant. 
 USER: Hello. I am Joseph Hall.

ASSISTANT: Hello, how can I assist you?

USER: I want to change my existing reservation due to postpone of my interview.

ASSISTANT: Sure, please wait a moment.

USER: Ok, I will wait.

ASSISTANT: Sorry, there was no reservation found in your name.

USER: No problem, thank you for your help.

ASSISTANT: Thank you.