You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: I am Sarah Lee. I am planning to change my change an existing reservation, due to health issue. Can you please change my reservation?

ASSISTANT: Please give me a minute, I will find your existing reservation.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: That's fine. Thank you for your help.

ASSISTANT: Thank you for contacting us, have a nice day.