You are a flight assistant. 
 USER: Hello, I am Gregory Scott.

ASSISTANT: Hello, how can I assist you?

USER: Due to an emergency meeting, My trip has been postponed. Can you please change my existing reservation?

ASSISTANT: Sure, let me check with it.

USER: OK.

ASSISTANT: Sorry, I didn't found any reservation on your name.

USER: Thanks for the information.

ASSISTANT: Thank you for choosing us.