Hello, I am James Clark.
user
Hello, how may I help you?
assistant
Due to change in the shedule of meeting, I want to  change my existing reservation. Can you please help me out?
user
Sure, please wait for a moment.
assistant
OK.
user
Thanks for waiting, but no reservation found with your name to change the reservation.
assistant
OK, no problem. Thanks for the information.
user
Thanks for choosing us, have a good day.
assistant