Investigation of unjust discriminatory rates, schedules, or services; no order to be entered without formal hearing.

Upon its own initiative or upon reasonable complaint made against any public utility that any of the rates, tolls, charges, or schedules, or services, or time and conditions of payment, or any joint rate or rates, schedules, or services, are in any respect unreasonable or unjustly discriminatory, or that any time schedule, regulation, or act whatsoever affecting or relating to the conduct of any street railway or common carrier, or the production, transmission, delivery, or furnishing of heat, light, water, or power, or any service in connection therewith, or the conveyance of any telegraph or telephone message, or any service in connection therewith, is in any respect unreasonable, insufficient, or unjustly discriminatory, or that any service is inadequate or cannot be obtained, the Commission may, in its discretion, proceed, with or without notice, to make such investigation as it may deem necessary or convenient of any public utility. But no order affecting said rates, tolls, charges, schedules, regulations, or act complained of shall be entered by the Commission without a formal hearing.