I'm using Cingular Wireless, in Tampa, FL.
The information for Houston, TX appears to be the same as that here in Tampa, FL.
If anyone would like to test this before adding, feel free to make contact with me in any of the following ways, prior:
home email: xial at livejournal dot com
home phone: +1 813 839 9339, ask for Justin.
The reason I need pre-test contact is simple: my house blocks most cellular signals. I'd need to get outside with the phone, else your tests will fail... ^^;
the testing target is
8133622256 at mobile.mycingular.net