You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: May I know your name please?

USER: My name is Dorothy Walker.

ASSISTANT: Sorry to say, there is no reservation on your name in our database.

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

ASSISTANT: Thank you for opting us.