Every public utility shall file with the commission, within a time fixed by the commission, schedules, which shall be open to public inspection, showing all rates, tolls and charges which it has established and which are enforced at the time for any service performed by it within the state, or for any service in connection therewith, or performed by any public utility controlled or operated by it. The rates, tolls and charges shown on such schedules shall not exceed, without the consent of the commission, the rates, tolls and charges in force January 1, 1913.
IC 8-1-2-38