My friend gave me an used Motorola XT557. HW V4.0. It was a Republic Wireless phone and he is not using it anymore and his contract expired. Because it is a CDMA phone, can I use it with other CDMA carriers? such as Verizon, Sprint, or those CDMA prepaid wireless providers? Or I have to tweak the OS/ROM in order to do that? Thank you for your help.