GSM-network is used for communicating a terminal with the data center (server), mainly GPRS/EDGE-communication channels, and in addition – the SMS channel. For this purpose SIM card is installed in GPS-tracker. It can be a SIM card purchased from any telecom operator or a SIM card purchased with a device, provided by the operator of monitoring services.
If you need to change the SIM card in the device, you will need to write a new phone number to change the settings. You can do this in the appropriate panel: