Apple iPhone 5 Unlocked Cellphone

Apple iPhone 5 Unlocked Cellphone, 16GB,

Unlocked cell phones are compatible with GSM carriers like ATT and T-Mobile, phones will NOT work with CDMA Carriers like Sprint, Verizon, Boost or Virgin. Please contact your provider before purchasing to ensure 100% compatibility. Product Description A slim and stylish design makes the Apple iPhone 5 smartphone lightweight and easy-to-carry around. Language Support: English (U.S.), English (UK), Chinese (Simplified), Chinese (Traditional), French, German, Italian, Japanese, Korean, Spanish, Arabic, Catalan, Croatian, Czech, Danish, Dutch, Finnish, Greek, Hebrew, Hungarian, Indonesian, Malay, Norwegian, Polish, Portuguese, Portuguese (Brazil), Romanian, Russian, Slovak, Swedish, Thai, Turkish, Ukrainian, Vietnamese

The iphone came quickly, but after inserting the nano-simcard, we realize the iphone is locked and attached to At&T network, it means that works only with AT&T network. What can I do to unlock it? the Iphone is now in colombia because it was supposed to be a gift.