From ABC News, but I've seen a similar story elsewhere:
"There are 300 million third-party charges totaling $2 billion on U.S. phone bills each year, according to the Senate Commerce Committee.
What's more, according to the Federal Communications Commission, about 15 million to 20 million households are overcharged for their telephone landlines by third-party companies but only 5 percent realize they are victims."
Here's the article: "Phone Bill Fees: How to Identify 3rd-Party Charges and Protect Yourself".
The article seems to focus on landlines. Does that mean that this problem does not occur with cell phones? That would be good to know?