You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Myself John Roberts.

ASSISTANT: How can I serve you Roberts?

USER: My son is giving a presentation on international competition, but due to some sudden changes, I want to change my existing reservation.

ASSISTANT: Sure, let me check with your previous reservation.

USER: Ok.

ASSISTANT: Sorry to tell you that no reservation was found by your name.

USER: Thank you for the information.

ASSISTANT: Thank you for choosing us. Have a nice day.