USBI - Zero Plus Dialing Modem dialer scam Internet

I'm getting ready to pay my monthly phones bills for my home and business through SBC like normal. And noticed USBI and Zero Plus Dialing Inc billed my for calls to United Kingdom and Reno, NV for just a few minutes a piece and these bills rang up over $100 to my home and $200 to my buiness? Later I called SBC and there were aware of these scams after having several other calls that day she said. They refused the charges being an unathorized service charge. She also signed me up for cramming protection on my phone lines. Although I'm sure I'll have to be sure in checking my bills here after now. I also called the companines in question.

One company (which are probally the same)
was ok and told me they'll take the charges off and put a block on the number. The other company the lady was EXTREMELY rude (I wish I'd gotten her name, I'm going to call back to get her name) and she also asked what SBC said to the exact word? But she took the charges off too and put a block on that number. Well how do we get the modem dialer off our computers? And WHY is this allowed? I know if I ripped off my customer I wouldn't be in business, so WHY are they allowed to still be in business?

Trent
Trenton, Ohio
U.S.A.