You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How may I help you?

USER: I need to change my existing reservation.

ASSISTANT: OK,Sure may I know your name please?

USER: Sure,My name is Deborah Lopez.

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

USER: OK,Thank you.

ASSISTANT: Thank you. Have a great day.