Minnesota regulators are investigating Frontier Communications after receiving a flood of customer complaints about the phone and internet provider.

The Minnesota Public Utilities Commission (PUC) recently opened an inquiry after "receiving a large volume of complaints related to the service quality, customer service, and billing practices of Frontier Communications," according to a regulatory filing. "After attempts to mediate these complaints, many of them remain unresolved."

The PUC asked the Minnesota Department of Commerce and the state Attorney General's Office to investigate and determine whether Frontier is complying with PUC rules. Both departments represent the public interest on matters before the PUC.

Stamford, Conn.-based Frontier said in a statement that it "is committed to our customers in Minnesota and is working with the Public Utilities Commission to resolve this matter. We strive to address billing issues and service complaints promptly."

Frontier, a large publicly traded company, also said that in recent months, it has updated its billing software and made "process improvements" and will continue to do so.

Frontier is the second largest landline phone company in Minnesota, operating as both Frontier and Citizens Telecommunications, according to the Commerce Department. With more than 98,000 landlines, Frontier serves parts of northeastern and southern Minnesota as well as Rosemount, Apple Valley, Farmington and Burnsville in the metro area.

In a November article, the Timberjay newspapers in Ely and Tower chronicled "dozens" of complaints about Frontier's service, including overbilling and long waits on hold for customer service. Also in November, Rep. Rob Ecklund, DFL-International Falls, put out a news release telling constituents to take their issues with Frontier to the PUC.

"I'd heard a bunch of complaints of poor service all across my district," Ecklund said. "I am a Frontier customer myself, and the service has been lousy," though he noted it improved last year after Frontier made some network upgrades.

Ecklund said most complaints he has fielded are about internet outages.

The state's initial investigation and report on Frontier is due on May 11.