You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Gregory Brown.

ASSISTANT: How can I help you for the day?

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

ASSISTANT: Sure, I am here to help you with this reservation change.

USER: Thank you.

ASSISTANT: Please wait for a moment, let me check your previous reservation status.

USER: Sure, I will wait for your information.

ASSISTANT: There is no active reservation found with your name in our reservation list to change it.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for reaching us.