Yes, it is. On november 26-2006, the U.S. Copyright Office ruled that consumers can legally unlock their cell phones in order to use them with rival carriers. Sometimes you might be able to ask your network to provide you with an unlock code. However, they will only do this for free if you have completed your contract. Obviously most networks don't want you moving away from their network so they will often charge extortionate rates to unlock your cell phone and you can also be made to wait up to 3 weeks to receive your unlock codes.
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