1.  Complaint.  The Commission may institute or any public utility may make complaint as to any matter affecting its own product, service or charges, with like effect as though made by any 10 persons, firms, corporations or associations.  

2.  Reparation or adjustment where utility admits excessive rate.  The commission may authorize reparation or adjustment where the utility admits that a rate charged was excessive or unreasonable or collected through error, and where it further appears that the utility, within 90 days after the rendering of any service within the State under such rate, has filed a reduced rate in place of the rate which admittedly was excessive or unreasonable or collected through error.  

3.  Reduced rates; amount of reparation.  The reduced rate published in accordance with this section shall continue in force one year unless sooner changed by the order or with the consent of the commission, and the amount of reparation which may be authorized by the commission shall not exceed the difference between the charges based on the reduced rate and the charges based on the rate canceled by the reduced rate.  

4.  Statute of limitations for complaints brought under this section.  Within 2 years after the rendering of any service within the State by a public utility, for which service a rate, toll or charge is made by the utility, a person aggrieved may complain to the commission that the rate, toll or charge exacted for the service is unjustly discriminatory against that person, either because it is higher than that charged by the same utility for the same service or service of similar value and cost rendered to other users or consumers, or because the utility has failed, without reasonable cause, to make a more favorable rate, toll or charge published by it for the same or similar service applicable to the user or consumer or to the class of users or consumers to which that person belongs, or at the place at which the service is rendered.  

5.  Complaint received within 6 months after reparation or adjustment ordered.  Within 6 months after an order has been made authorizing reparation or adjustment under subsections 2 and 3, any person aggrieved may complain to the commission that the person is entitled to reparation from the same utility because the person paid the rates that the utility admits are excessive or unreasonable or collected through error, provided the utility might lawfully have made the reparation on its own petition, and provided the person has made a written request for the utility to file its own petition for authority to make the reparation or adjustment not less than 30 days before filing a complaint with the commission.  

6.  Commission investigation to determine whether to hold a hearing.  Upon receipt of a complaint, the commission shall investigate as it determines necessary to determine whether a hearing ought to be held.  

7.  Notice of hearing.  The commission may order a hearing upon such notice to the utility as it determines just and reasonable.  

8.  Commission decision after hearing; refund.  If, after the hearing, the commission decides that the complainant has been injured by paying rates which the utility admits are excessive, unreasonable or collected through error, it shall determine the sum that the utility ought to refund or repay to the complainant, which sum the utility has the right to refund.  

9.  Utility refusal or neglect to make refund; court action.  If the utility refuses or neglects to make the refund within 30 days, the party aggrieved may maintain an action in the courts of the State to recover the amount. In the trial the findings of the commission are prima facie evidence of the truth of the facts found by it, and no utility may avail itself of the defense of the action that the service involved was in fact made on the published schedule rate in force at the time it was rendered.  

10.  Utility that complies may not be held liable.  No utility making a refund upon the order of the commission or pursuant to judgment of the court may be liable for any penalty or forfeiture or subject to any prosecution under the laws of this State on account of making the refund.