A Montana man has pleaded guilty to wire fraud and money laundering after prosecutors said his companies ran up $70 million in unauthorized charges on phone bills across the nation in a "cramming" scheme.

The U.S. Attorney's Office says cramming involves tricking customers into paying for services they didn't authorize or receive.

They say 59-year-old Steven Sann's case involved voicemail accounts people may have unwittingly signed up for while answering questions on websites offering free products or job-search assistance.

Authorities say hundreds of complaints about monthly charges from $9.95 to $24.95 led Sann's companies to return more than $40 million.

Sann faces up to 30 years in prison. He was released pending sentencing in July. His attorney, Peter Lacney, didn't immediately return a phone message seeking comment Monday.