You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

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

ASSISTANT: Sure, can I know your name please?

USER: My name is Joseph Lee.

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

USER: That's fine. Thank you for your information.

ASSISTANT: Thank you for approaching us.