You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you now?

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

ASSISTANT: Sure, I am oblige to help you with that. Can I know your name to check your previous reservation?

USER: Myself Timothy Hall.

ASSISTANT: Please be on hold.

USER: Ok.

ASSISTANT: We regret to inform you that, there is no reservation found on your name in our reservation list.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for approaching us, hope you have a great day.