Frontier Communications has failed to provide adequate, reliable phone and internet service to its Minnesota customers, according to an investigation by the Minnesota Commerce Department.

The investigative report was filed with the Minnesota Public Utilities Commission on Friday, Jan. 4.

The report recommends that Frontier be required to refund or credit customers for service outages and unauthorized charges; add staffing to improve customer service; and increase investments in infrastructure and equipment.

The investigation focused on the service quality, customer service and billing practices of Frontier Communications of Minnesota, Inc., and its affiliate, Citizens Telecommunications of Minnesota, LLC. They provide landline phone service to nearly 100,000 Minnesota households and businesses, as well as internet service, in parts of northeastern Minnesota, southern Minnesota and the Twin Cities metro.

As part of the investigation, seven public hearings were held last fall in Frontier’s service area.

The report is based on more than 1,000 consumer complaints and statements, as well as Frontier’s responses to information requests by the Commerce Department.

The report is available at mn.gov/commerce.