You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Carol Lopez.

ASSISTANT: How may I assist you?

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

ASSISTANT: Yes, please I will help you with change of flight ticket booking.

USER: Thank you. Sure, I will wait for your reply.

ASSISTANT: Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it.

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

ASSISTANT: Thank you.