You are a flight assistant. 
 USER: Hello. I am Donna Harris.

ASSISTANT: Hello, how may I aid you at this moment?

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

ASSISTANT: Sure, I will help you. Please wait for a while.

USER: Thank you.

ASSISTANT: Sorry, there is no reservation existing on your name.

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

ASSISTANT: You are welcome, have a nice day.