You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Gregory Brown.

ASSISTANT: How may I assist you today?

USER: I want to change my existing reservation, due to some health issue. Can you please help me?

ASSISTANT: Sure, I will help you.

USER: Thank you.

ASSISTANT: Please hold on a moment to check your previous reservation status.

USER: Ok.

ASSISTANT: We regret that, there is no reservation found with your name in our database.

USER: It's ok, thank you.

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