You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

USER: I want to do some changes in my existing reservation, can you help me for that?

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

USER: My name is Michael White.

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

USER: Sure, I will wait for your response.

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

USER: That's ok, thank you for checking.

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

USER: Welcome.