Three of the top four US wireless companies — AT&T, Sprint and T-Mobile — have agreed to stop billing American customers for the spam texts that millions of people have been tricked into receiving and sending out in recent years. The move, which could take a few days or weeks to go into effect, was announced Thursday afternoon by the Attorney General for Vermont, William Sorrell, who worked with the attorneys general from 44 other states to coordinate the anti-spam initiative. "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," Sorrell said. "We’re hopeful the other carriers will soon follow their lead."

An AT&T spokesperson confirmed that the company was onboard with the plan, writing: "AT&T has decided to discontinue billing for premium SMS content." T-Mobile CEO John Legere also tweeted about the change on Thursday afternoon, writing: "We believe in making things right for our customers," and linking to T-Mobile's website, which now includes the promise: "T-Mobile will terminate all billing for premium SMS, except for charitable and political giving, as soon as possible with as minimal impact on our customers as possible." Conspicuously absent from the list of carriers involved was Verizon, the nation's single-largest wireless carrier by customer base. A Verizon spokesperson provided us the following statement explaining why the company had not joined in the effort, saying it was in the process of "winding down" its premium message service:

"While we don’t agree with all of the Attorney General’s allegations, we respect his efforts in this area. For years, Verizon has been vigilant in protecting our customers from bad actors. There have been numerous times we have terminated programs and in some cases have taken aggressive legal action in order to ensure our customers were protected. Since premium messaging was first introduced, technology advances and smartphone adoption have dramatically changed the way customers access information. Verizon had previously decided to exit the premium messaging business because of these changes as well as recent allegations that third parties have engaged in improper conduct in providing premium messaging services to our customers. We are in the process of winding down our premium messaging business. Verizon will, however, continue to support text-to-donate for charitable programs and text-to-contribute for political campaigns that use this technology."

AT&T and T-Mobile are the first to officially confirm that they're eliminating all charges for so-called "premium SMS" services, which allow customers to subscribe to services that text them and prompt them to text back. In reality, many of these services are little more than malware operations that trick people into downloading apps or subscribing to services that send out texts to shady companies without the user's knowledge, which then charge the sender's phone bill for the service.

The US Federal Communications Commission has tried to cut down on spam texts by implementing new policy and filing lawsuits against some of the major sources of text spam. The agency has been trying to limit spam texts using new laws and no-call lists since the dawn of the mobile device era back in 1991, but to little avail. As T-Mobile notes on its website: "Despite protections and processes put in place by T-Mobile and the industry, not all premium SMS vendors have acted responsibly."  That explains the drastic moves today to eliminate charges going forward for all wireless customers who receive spam texts. Previously, wireless customers would have to forward texts or complain to wireless carriers directly to get refunds for texts they didn't want.

SMS, or short messaging service, is the main text message service found on most mobile devices, although many customers use apps like WhatsApp to circumvent SMS. Apple's iMessage and Google's Hangouts also have their own proprietary servers that don't allow for the same type of spam marketing or advertising texts to get through.

Updated to add comment from Verizon.