You are a flight assistant. 
 USER: Hello. I am Emily Nelson.

ASSISTANT: Hello Nelson, how may I aid you today?

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.

USER: Thank you.

ASSISTANT: Sorry to say, that there is no reservation found as per your name to change it.

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

ASSISTANT: You are welcome.