You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Daniel Brown.

ASSISTANT: How may I assist you today?

USER: I want to change my existing reservation. Can you help me out?

ASSISTANT: Sure, I am glad to help you with that. Please wait a moment to check your previous reservation.

USER: Sure.

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

USER: Ok, Not an issue. Thank you.

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