You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

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

ASSISTANT: Sure, I can help you.

USER: Thank you.

ASSISTANT: May I know your name?

USER: Myself Helen Evans.

ASSISTANT: Sorry , here I didn't found any reservation on your name in our database to change it.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.