A method of reporting a result of service option re-negotiation to a mobile switching center of a CDMA communication services is disclosed. An assignment completion message structure or a service option report message structure is used to report the changed service option. The method using the assignment completion message structure includes transmitting a message type, a channel number representing a communication path being used, encoded information, and contents of the changed service option. Also, the method using the service option report message structure includes transmitting a message type and the contents of the changed service option.