HELENA, Mont. (AP) — The Montana Supreme Court has upheld the certification of a class-action lawsuit against the city of Billings over franchise fees charged on residents’ water, sewer and garbage bills.

The plaintiffs argue the fees, which were ended in mid-2018, constitute an illegal sales tax and they are seeking reimbursement.

District Judge Gregory Pinski certified the case as a class action involving up to 35,000 people last April. The city appealed and the Supreme Court upheld his ruling on Tuesday.

The wastewater class includes people who paid the franchise fee dating back to Jan. 18, 2010 and the garbage class paid fees dating back to July 1, 2012.

Justices and the plaintiffs agreed the claims over the water franchise fees could date back only to February 2014 after the city argued that water is a “good” and a four-year statute of limitations applies. The Supreme Court said the District Court may modify the start date of the water class. The case is remanded to District Court for further action.

Billings started charging franchise fees in 1992; 4% for water and wastewater services and 5% for solid waste disposal services.

During the 2016-17 fiscal year, the plaintiffs said the city collected more than $2.3 million in franchise fees and used the money to help fund parks, municipal court and public safety, The Billings Gazette has reported. The city argued the fees were part of the utility rate.