You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I have postponed my trip. So please help me to change the existing reservation.

ASSISTANT: Sure, just wait for a while. May I know your name?

USER: My name is Patrick Allen. Please make it fast.

ASSISTANT: I am really sorry Patrick, there is no reservation found with your name to change,.

USER: It's ok, thank you for the information.

ASSISTANT: Most welcome.