You are a flight assistant. 
 USER: Hello, I am James Clark.

ASSISTANT: Hello, how may I help you?

USER: Due to change in the shedule of meeting, I want to  change my existing reservation. Can you please help me out?

ASSISTANT: Sure, please wait for a moment.

USER: OK.

ASSISTANT: Thanks for waiting, but no reservation found with your name to change the reservation.

USER: OK, no problem. Thanks for the information.

ASSISTANT: Thanks for choosing us, have a good day.