You are a flight assistant. 
 USER: Hello, I am David White.

ASSISTANT: Hello, how may I assist you today?

USER: Due to sudden changes, my seminar has been postponed. So I need to change my reservation. Can you please help me with it?

ASSISTANT: Sure, we are here to help you. Please wait a moment.

USER: OK.

ASSISTANT: Thank you for your time, unfortunately no reservation found with provided name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for availing us.