After you have applied for a monitoring plan, you have to activate your GSMVLP5-4G Cellular Communicator with your Honeywell AlarmNet dealer before it will work with your L5100 Security System. Contact your dealer, and they will activate the sim card for you. This will allow your cellular communicator to send alarm signals to your central monitoring station. Not only that, but it qualifies you for Honeywell's interactive Total Connect Service. Total Connect lets users arm/disarm their security system, lock/unlock doors, monitor security camera feeds, and even receive text and email alerts all from a smartphone or computer with an internet connection.