You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I have changed my plan. So please help me to change the existing reservation.

ASSISTANT: Sure, may I know your name please?

USER: My name is Laura Young.

ASSISTANT: Sorry to say this Laura, there are no flights booked with your name.

USER: That's ok, thank you for searching for the details.

ASSISTANT: You are welcome. Have a nice day.