From the FTC's press release:

In a complaint filed today, the Federal Trade Commission is charging mobile phone service provider T-Mobile USA, Inc., with making hundreds of millions of dollars by placing charges on mobile phone bills for purported “premium” SMS subscriptions that, in many cases, were bogus charges that were never authorized by its customers.

The FTC alleges that T-Mobile received anywhere from 35 to 40 percent of the total amount charged to consumers for subscriptions for content such as flirting tips, horoscope information or celebrity gossip that typically cost $9.99 per month. According to the FTC’s complaint, T-Mobile in some cases continued to bill its customers for these services offered by scammers years after becoming aware of signs that the charges were fraudulent.