I see no point in using this device. Since it uses your own internet connection, you might as well just use the free Whistle phone app in your home instead. It uses your home wireless network and in the same way but doesn't charge you for calls, including long distance.
Granted this app gives you a new number, but still is perfect for making outgoing calls with.
what is the point of paying for att service if all your going to do is use wifi, i have no att reception at my house so i figured its free and why not, now i get great fast service and use the same number, done and done