A Subscriber Identity Module (SIM) card is a portable memory chip used mostly in cell phones that operate on the Global System for Mobile Communications (GSM) network.

The phones comes in both locked and unlocked with sim.If it is a locked phone you need to unlock it with current sim card to use it with all GSM network Sim card.You can unlock it easily by using an unlock code.You can get this code at reasonable cost from ClassicUnlocking.com with easy step by step unlocking instructions.This is the fast and permanent unlocking method.