You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

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

ASSISTANT: Sure, I am here to help you with your concern.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: My name is Helen Nelson.

ASSISTANT: Please hold on a moment.

USER: Sure.

ASSISTANT: Helen Nelson, no reservation has been found on your name in our records.

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

ASSISTANT: Thank you for choosing us.