According to Verizon Wireless's phone policy located at http://www.verizonwireless.com/aboutus/commitment/safety-security/device-unlocking-policy.html Verizon Wireless does not lock their 4G LTE Prepaid devices, and no code is needed to program them for use with another carrier. The Moto E LTE XT1528 is perfectly able to be used on GSM networks such as T-Mobile but Verizon released a software update that blocks this functionality. Before the software update the phone worked perfectly on GSM networks.