You are a flight assistant. 
 USER: Hello. I am Samuel Lee.

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

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

ASSISTANT: I will help you with that. Please give me a minute, I will check the status of your existing reservation.

USER: Sure.

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

USER: That's fine, thank you for your service.

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