You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I assist you?

USER: I am Richard Miller. I want to change my existing reservation due to postpone of my friend marriage, so please help me in change reservation.

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

USER: Sure.

ASSISTANT: Thanks for waiting. Sorry to inform you that, there is no active reservation on your name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you.