You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I want to change my existing reservation, because of some health issues. Can you please help me in this condition?

ASSISTANT: Sure, may I know your name please as it is mandatory to know your name for changing the reservation.

USER: Sure, my name is Nancy Turner here.

ASSISTANT: Ok, hold on for a while. Let me check in our data base.

USER: Sure.

ASSISTANT: Sorry Nancy, there are no flight reservation found under your name.

USER: Ok, no problem.

ASSISTANT: Thank you for availing our services. Have a nice day.

USER: You are welcome.