You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist  you now?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, can I have your good name please to check your  reservation status?

USER: My name is Nicole Lewis.

ASSISTANT: Ok,  please wait a moment.

USER: Sure.

ASSISTANT: Sorry Nicole Lewis, no reservation has found under your name to change.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us, have a good day.