You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: My name is Brian Johnson. I want to change my existing reservation, due to bad weather in New York.

ASSISTANT: Sure, I will help you with that.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found under your name Brian.

USER: That's ok, thanks for your information.

ASSISTANT: Most welcome.