When you connect to ST with an ATT flavor SIM the network pushes the carrier string to your phone and labels itself "Home."
It is just a name. My phone says "Home" and it works anywhere I take it.
If your phone is not connecting when you step out of the house, you have another issue. Sign up for the site if you need to reply in this thread.
Does voice work when you go down the street?
Does data work? Turn off WiFi and test this.
Here are what your settings should be:
http://forums.windowscentral.com/nok...ml#post2933337