Verizon Wireless and Sprint have agreed to pay a combined $158 million to settle allegations that they hit cellular customers with unauthorized third-party charges, a practice known as "cramming." Most of the money will go toward giving customers refunds.

The Federal Communications Commission and Federal Trade Commission announced the settlements today. Previously, federal regulators forced T-Mobile US and AT&T to pay $90 million and $105 million, respectively, over similar allegations.

Investigations revealed that Verizon and Sprint "billed customers millions of dollars in unauthorized third-party premium text messaging services [PSMS], a practice called 'cramming,'" the FCC said. "The monthly charge for these third-party premium text messaging services ranged from $0.99 to $14.00, but typically were $9.99 per month. Verizon retained 30 percent or more of each third-party charge that it billed, while Sprint received approximately 35 percent of collected revenues for each of its third-party charges. Numerous consumers have complained to the FCC, other government agencies, and the carriers that they never requested or authorized the third-party services for which they were charged. Customers who called to complain were often denied refunds, and yet, when the FCC requested proof that customers had authorized charges, the carriers were unable to prove that these services were ever requested."

Verizon will pay $90 million, with $70 million being distributed to customers in refunds. Sprint will pay $68 million, including $50 million in refunds to customers. The remainder goes to state governments that participated in the settlement negotiations and to the US Treasury.

The major carriers agreed to stop the fraudulent billing in late 2013, but the settlements with Verizon and Sprint say the practice continued into 2014. The settlements require the carriers to "no longer offer commercial third-party PSMS charges; obtain informed consent from customers prior to allowing third-party charges; clearly and conspicuously identify third-party charges on bills; offer a free service for customers to block all third-party charges; [and] regularly report to the FCC on compliance and refunds to customers."

Current and former Verizon customers can submit claims for refunds here, and Sprint customers here, for unrefunded PSMS charges billed since July 1, 2010. The deadline is December 31, 2015. "Consumers with questions about the redress programs can call 1-877-389-878 for the Sprint case or 1-888-726-7063 for Verizon," an FCC spokesperson told Ars.

There are also websites for AT&T and T-Mobile customers to request refunds.