You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you now?

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

ASSISTANT: Sure, may I know your name please?

USER: Sure, my name is Anna Robinson.

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

USER: That's fine, thank you.

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