SIMlock is a blocking code for the restricted use of SIM cards. This blocking code prevents a cell phone of a SIM card or a prepaid card of a certain service provider or network operator from being operated with a SIM card of another network operator.
Providers can also use it to restrict the use of certain services, for example, it can prevent the use of prepaid cards of other service providers, the use of the cell phone in certain countries or networks. The latter, the blocking of certain networks is called netlock. Only after the blocking period has expired can the blocking code be lifted by the network operator. Such a blocking is called a netlock.
In the case of SIM lock, the cell phone reads the SIM card data and compares it with the data stored in the cell phone. If there are any discrepancies, the SIM lock kicks in. SIM lock can also refer to the SIM card itself, so that only SIM cards or prepaid cards of a certain provider can be used. This is referred to as full card SIMlock.