Applications and complaints may be made by any corporation, public or private, person, chamber of commerce or board of trade, by any civic, commercial, mercantile, traffic, agricultural or manufacturing association or by any body politic, commission, board or municipal corporation by petition or complaint in writing, setting forth any act or thing done, or omitted to be done, with respect to which, under the provisions of Articles 1, 3 and 5 of this chapter, the Commission has jurisdiction or is alleged to have jurisdiction. But the Commission may at its discretion refuse to entertain a complaint as to the reasonableness of any rates or charges unless it be signed by the mayor or the president or chairman of the board of trustees or a majority of the council, commission or other legislative body of the city or county or city or town affected by the subject matter of such complaint or by not less than twenty-five consumers of the public utility named in the complaint. Any public utility shall have the right to petition or complain to the Commission on any of the grounds upon which complaints and petitions are allowed to be filed by other parties, including the fairness, reasonableness or sufficiency of any schedule, classification, rate, price, charge, fare, toll, rental, rule, regulation, service or facility of such public utility and in such event the same procedure shall be adopted and followed as in other cases or the complaint may be served upon any parties designated by the Commission.