With an unlocked phone, you simply plug in a different SIM card to change service providers. Simple, easy, and instantaneous. This works with GSM phones ( At&t & T-Mobile) and a hand full of Verizon phones that have a sim card.
There are three main reasons why you might want to unlock your phone.
Tmobile, AT&T, Cricket, Metro PCS, Family Mobile, Simple Mobile, Net 10, Red Pocket, Straight Talk, H2o, & lots more. There are more company's starting to switch over to the GSM phones that can be unlocked, giving you more and more options to use the phone you already have with some other company.
Unlocking: Designed for multi-sim card use only. No (MMS) multi-media service provided. 3G Mobile is not Responsible for black listed phones or Icloud locked phones. No refunds are applicable if device is black listed before or during unlock process. Unlocks are Non-Cancellable. Refunds only if code is not found in server.