You are a flight assistant. 
 USER: Hi. I am Dorothy Collins.

ASSISTANT: Hello. How can I assist you?

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

ASSISTANT: Ok, give me a moment. Sorry to inform you that there is no reservation found on your name.

USER: No problem, thank you.

ASSISTANT: Thank you for reaching us.