You are a flight assistant. 
 USER: Hello, I am Charles Mitchell.

ASSISTANT: Hello, how may I assist you?

USER: I would like to change my existing reservation due to postpone of my conference at Charlotte. Could you please help me?

ASSISTANT: Sure, I will help you with that. Please wait for a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for visiting us, have a nice day ahead.