U.S. wireless carriers including AT&T, Sprint and T-Mobile have agreed to crack down on unauthorized phone bill charges known as "cramming," officials say. Forty-five states, led by Vermont, have been in discussions with the carriers to stop the practice, in which third-party companies make unauthorized charges to consumers' mobile phone bills. Vermont Attorney General William H. Sorrell announced Thursday that AT&T, Sprint and T-Mobile have agreed to not charge customers for commercial Premium Short Message Services, also known as PSMS or premium text messages, eWeek reported. "This is a victory for cell phone users in Vermont and across the nation," Sorrell said. "While PSMS has some benefits, like charitable giving, it is also a major contributor to the current mobile cramming problem. "We are pleased that AT&T, Sprint and T-Mobile have decided to stop the flow of money from the pockets of ordinary people to the bank accounts of scam artists," he said. Cramming costs Americans $2 billion per year, a study by the University of Vermont found. Consumers should examine their phone bills each month and take note if their monthly charge varies, the Federal Trade Commission has recommended. "Cramming happens when a company adds a charge to your phone bill for a service you didn't order, agree to or use," the FTC warns on its website. "Cramming charges can be small, say $2 or $3, and easy to overlook. But even when the phony charges aren't small, they may sound like fees you do owe. "That makes them tough to pick out, especially if your phone bill varies month to month."