You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I respond to your request?

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

ASSISTANT: Sure, we are here to help you to change your reservation. Let me know your name, to check with your previous reservation list.

USER: Myself Anthony Moore.

ASSISTANT: Thanks for providing, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry to notify you that, we did not found any active reservation on your name to change it.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for approaching our service.