Connect your T-Mobile phone to the PC via a USB cable.
Is using a third-party tool like Vario legal? In many jurisdictions, including the United States, unlocking a phone you fully own is entirely legal under the Unlocking Consumer Choice and Wireless Competition Act. However, there are a few nuances to keep in mind: VARIO UNLOCK TOOL TMOBILE-MOBILE PHONE
The most notable tools developed by the XDA Developers community included: Connect your T-Mobile phone to the PC via a USB cable
Flashing incorrect files or losing connection mid-process can permanently corrupt the device firmware. including the United States