You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I am Virginia Evans. I want to change my existing reservation due to postpone of my client meeting, so please change my existing reservation.

ASSISTANT: Please wait for a while, let me check and revert to you.

USER: Sure.

ASSISTANT: There is no reservation found with your given name.

USER: Ok, no problem.

ASSISTANT: Thank you for choosing us.

USER: Thank you.