These BlackBerries support UMA calling, not Wi-Fi calling. What is the difference, you may ask? UMA is a protocol that allows access to GSM services over the unlicensed spectrum. This could be over Wi-Fi or bluetooth or any other method. However, UMA on BlackBerries is restricted to being over Wi-Fi I believe. Wi-Fi is the physical link, and UMA is the protocol used to communicate with GSM providers. You cannot use the phone for free over UMA without a carrier to connect to, but you could perhaps get some VOIP application if there is one available that works over Wi-Fi and IP (instead of GSM).