A SIM-Lock, NETWORK LOCK, carrier lock, imei lock or (Master) subsidy lock is actually a technical limitation built into GSM and CDMA mobile devices by manufacturers for use by carriers to restrict the usage of these phones to a particular countries and/or networks. This is as opposed to a mobile phone (retrospectively called SIM-free or unlocked) that doesn't impose any SIM constraints.
The vast majority of cellular phones can be unlocked to work with any GSM network provider, however phone may still display the original logos and may not support features of the new service provider. In addition to the locking, phones may also have firmware that come with them which is specific to the network provider. This firmware is installed by the service provider which is separate from the locking mechanism. The majority of cell phones can be unbranded by re-flashing a different firmware type, a process recommended for advanced users only. Unlocking Technology:
A handset can be unlocked simply by entering a code supplied by the service operator. Alternative mechanisms incorporate software working on the device or a pc attached to the handset, hardware devices that connect to the phone or over-the-air by the service provider. Most of the time the unlock operation is permanent. The code needed to do away with all locks from a cell phone is known as the master code, network code key, or multi-lock code. Generally if the device is network locked it will usually show one of these messages: SIM network PIN blocked, Enter lock PIN. Economics:
The main reason to unlock a device is usually to be able to utilize it with another type of SIM card. Consumers may want to keep on using their smartphone but with a new service provider or while traveling abroad they may wish to connect to a foreign network by using a prepay subscription.Unlocking Services:
Many businesses provide a on-line unlocking service
. This service requires individuals who want to unlock a handset to give their IMEI number to a unlocking company and quite often they will also require the country and network the device is locked to, often sent via email or entered on their website. The company then will provide (at a cost to you) a unlock code for the mobile. Unlocking Service Providers:
Disappointingly there are a lot of fraudulent online retailers active in the cell-phone imei unlocking industry. As a consequence it is prudent to make sure you find a reliable provider for these services. To aid with the search for a trustworthy company, we have provided a checklist beneath (and in no specific order) of a few legitimate organisations currently offering such services.Reputable Mobile Phone IMEI Unlocking Service Providers: