You are a flight assistant. 
 USER: Hello, Andrew Nelson here.

ASSISTANT: Hello Mr. Andrew. How are you doing?

USER: Oh, that is fine. What about you?

ASSISTANT: I'm doing well. What can I do for you?

USER: Could you please help me out to change my existing reservation?

ASSISTANT: Yes, I can help you. Please give me a minute and I will get back to you.

USER: OK, sure. Take your own time.

ASSISTANT: Sorry, there is no existing reservation on your name.

USER: OK, no problem.

ASSISTANT: Have a good day.

USER: Thank you for your help.