You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you at this moment?

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

ASSISTANT: Sure, I will help you with that. May I know your name please?

USER: My name is Samantha Barker.

ASSISTANT: Please wait for a moment, let me check your previous reservation status.

USER: Sure.

ASSISTANT: Samantha Barker, there is no reservation found on your name in our reservation list to change it.

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

ASSISTANT: Thank you for reaching us. Have a great day.