(1) The commission shall proceed, with or without notice, to make such investigation as it may deem necessary upon a complaint made against any public utility by any mercantile, agricultural, or manufacturing society or club; by any body politic or municipal organization or association, the same being interested; or by any person, firm, or corporation, provided such person, firm, or corporation is directly affected thereby, that:
(a) any of the rates, tolls, charges, or schedules or any joint rate or rates are in any way unreasonable or unjustly discriminatory;
(b) any regulations, measurements, practices, or acts whatsoever affecting or relating to the production, transmission, delivery, or furnishing of heat, light, water, power, or regulated telecommunications service, or any service in connection therewith is in any respect unreasonable, insufficient, or unjustly discriminatory; or
(c) any service is inadequate.
(2) No order affecting such rates, tolls, charges, schedules, regulations, measurements, practices, or acts complained of shall be entered without a formal hearing, except the commission may issue an order to provide service to a residential consumer pending a hearing on a complaint by such consumer or by the consumer counsel on behalf of such consumer against a public utility, providing that the hearing is held within 20 days unless further delayed by consent of all parties.