You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: My name is Gregory Collins.

ASSISTANT: I hope your doing well Collins.

USER: I planned a trip to New York, but unfortunately there is heavy snowfall in New York.

ASSISTANT: Ok.

USER: So I want to change my existing reservation.

ASSISTANT: Sure, please wait let me check your reservation details.

USER: Ok.

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

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

ASSISTANT: Thank you and have a nice day.