You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you for the day?

USER: Can you please help me out with changing my existing reservation?

ASSISTANT: Sure, I am here to help you with that reservation change. May I know your name please?

USER: Ok, my name is Joshua Miller.

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

USER: Ok.

ASSISTANT: Thank you for waiting, but I am very sorry to say that, there is no active reservation found on your name in our reservation list to change it.

USER: That's ok, thank you for the response.

ASSISTANT: Most welcome, thank you for reaching us. Have a great day.