69-3-330. Decision by commission. (1) If, upon a hearing and due investigation, the rates, tolls, charges, schedules, or joint rates are found to be unjust, unreasonable, or unjustly discriminatory or to be preferential or otherwise in violation of the provisions of this chapter, the commission may fix and order substituted the rates, tolls, charges, or schedules as are just and reasonable.

(2) If the commission determines that a rate, toll, or charge has been collected in violation of 69-3-305(1)(b), the commission may order refunds or credits as specified in 69-3-305(3).

(3) If the commission finds that any regulation, measurement, practice, act, or service complained of is unjust, unreasonable, insufficient, preferential, unjustly discriminatory, or otherwise in violation of the provisions of this chapter or that the service is inadequate or any reasonable service cannot be obtained, the commission may substitute other regulations, measurements, practices, services, or acts and make an order relating to it as is just and reasonable.

(4) In any decision ordering a change in the rates that may be charged for electricity or natural gas, the commission shall list each expenditure submitted by the utility for allowance as an operating cost that is disallowed by the commission as an element of operating costs. The list of disallowed expenditures must appear in the written decision of the commission and must itemize each expenditure by amount, category, and purpose.

(5) A party in interest who is aggrieved by a commission-contested case decision may petition for judicial review pursuant to the Montana Administrative Procedure Act in accordance with Title 2, chapter 4, part 7.