You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I am Christopher Gonzalez. My meeting at NASA space centre has been postponed, due to heavy snow-storms. Can you help me to change an existing reservation?

ASSISTANT: Sure, please wait a moment I will check the existing reservation and revert you.

USER: Ok.

ASSISTANT: Sorry there is no reservation found on your name.

USER: Ok, thanks for the information.

ASSISTANT: Thank you, have a nice day.