The suits, filed in conjunction with the Federal Trade Commission, alleges New Jersey-based Alyon Technologies violated advertising and telecommunications laws.
Wisconsin's lawsuit claims Alyon connected Internet users to the company's toll phone number when they tried to close Alyon's pop-up windows advertising porn sites.
The toll number charges $5 a minute, Attorney General Peg Lautenschlager said, resulting in bills ranging from $14 to more than $1,000.
"The way this organization has allegedly been doing business is illegal, irresponsible and an outrageous misuse of Internet technology," she said.
Other states that have sued are California, Connecticut, Florida, Illinois, Kentucky, Missouri, New Jersey, Ohio, North Carolina, Nebraska, Texas and West Virginia.
Alyon officials said Thursday that they alerted the FTC to procedures the states are questioning and have been working with state lawmakers to make sure its practices comply with federal and state laws.
"Given our willingness and effort to work to resolve the consumer issues, we are stunned by the FTC's decision to initiate this unwarranted action," Alyon president Stephane Touboul said in a statement.