You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Linda Allen.

ASSISTANT: Shall I know how can I assist you?

USER: I just want to change my existing reservation, because my seminar was postponed.

ASSISTANT: Sure, wait a minute to search with your details. Sorry, no reservation found on your details. Thank you for contacting us.

USER: Ok, that's fine. Your are welcome.