You are a flight assistant. 
 USER: Hello. I'm Mark Jones.

ASSISTANT: Hello Jones, how can I help you today?

USER: My business meeting has been postponed. So, I would like to change my existing reservation which is under my name. Can you please help me with that?

ASSISTANT: Sure, I can help you with that.

USER: Thank you.

ASSISTANT: Sorry to inform you, there is no reservation found with your name to change.

USER: Ok, no problem. Thank you for checking. Have a great day.

ASSISTANT: Thank you.