When complaint has been made to the Commission concerning any rate or charge for any electric current furnished or service performed by any electrical utility and the Commission has found after hearing and investigation that the electrical utility has charged an unreasonable, excessive or discriminatory amount for such electric current or service, the Commission may order that the electrical utility make due reparation to the complainant therefor, with interest from the date of collection; provided, however, that no unreasonable discrimination will result from such reparation. But no order for the payment of reparation upon the ground of unreasonableness shall be made by the Commission in any instance wherein the rate or charge in question has been authorized by law. No assignment of a reparation claim shall be recognized by the Commission except assignments by operation of law as in cases of death, insanity, bankruptcy, receivership or order of court. If the electrical utility does not comply with the order for the payment of reparation within the time specified in such order, suit may be instituted in any court of competent jurisdiction to recover the same, and upon trial of such suit a duly certified copy of the order of the Commission shall be prima facie evidence of the facts therein set forth. All complaints concerning unreasonable, excessive or discriminatory charges on which reparation orders may be made shall be filed with the Commission within two years from the time the cause of action accrues, and the suit for enforcement of the order shall be commenced in the court within one year from the date of the order of the Commission. The remedy in this section provided shall be cumulative and in addition to any other remedy or remedies in this chapter provided in case of failure of an electrical utility to obey an order or decision of the Commission.