Most of the mobile phones that are sold are locked by the service providers and users must buy the service providers package of the handset as well of the network service. With the No-Key Nokia X-SIM, one can unlock their phones and can change their mobile service providers according to their convinience. The No-Key Nokia X-SIM unlocks only Nokia phones that work on a SIM card. Actually the No-Key Nokia X-SIM doesn't unlock the phones, but just opens the phones by checking if the SIM card matches with the network operator. The X-SIM card then gives a signal to the Nokia phone similar to that of original SIM card. This just "opens" the phone helping it to operate in different network areas. Warranty and downloads from Nokia are guranteed.