You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you at this moment?

USER: I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: Myself John Campbell.

ASSISTANT: Ok, please be on hold.

USER: Ok.

ASSISTANT: Sorry we could not find any reservation on your name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for choosing us.