Whenever, upon any investigation of a public utility made by the state corporation commission, on its own initiative or upon complaint filed, the commission shall find that any rate, toll, charge or schedule or joint rate is unjust, unreasonable, excessive, insufficient or unjustly discriminatory or preferential or otherwise in violation of the public utility act; or that any measurement, regulation, practice, act or service is unjust, unreasonable, unsafe, insufficient, preferential or discriminatory or otherwise in violation of the public utility act; or it shall find that any service is inadequate or that any service that can reasonably be demanded is not being furnished; or when an investigation is necessary because of an application by a public utility and such application is not justified, the commission shall ascertain and declare and by order fix the expenses incurred by the commission upon such investigation and shall by such order direct such public utilities to pay to the state treasurer to reimburse the fund appropriated for the public service commission an amount to cover the expenses so incurred: Provided, That such order shall not become operative unless the matter in connection with which such investigation shall have been made shall have been finally determined, by appeal or otherwise, adversely to such public utility. The commission shall cause a certified copy of all such orders to be delivered to an officer or agent of the public utility affected thereby, and all such orders shall, of their own force, take effect and become operative twenty days after final determination of the investigation by appeal or otherwise: Provided, That if appeal is taken by any public utility a surety bond shall be furnished by such utility to secure the payment of such expenses in case the order of the commission shall be sustained.