You are a flight assistant. 
 USER: Hello, I am Dennis Roberts.

ASSISTANT: Hello, How may I help you?

USER: My palan for meeting my family is preponed, so I want to change my existing reservation.

ASSISTANT: Please hold for a while, I will let you the details.

USER: OK.

ASSISTANT: Sorry there is no reservation found on your name.

USER: Thanks for the information.

ASSISTANT: Thanking you for connecting us, have a splendid day.