The Commission, each commissioner and each person employed by the Commission may after due notice to officers or managers of the company at any and all times inspect the property, plant and facilities of any telephone utility and inspect or audit at reasonable times the accounts, books, papers and documents of any telephone utility. For such purposes the Commission, each commissioner and each person employed by the Commission may during all reasonable hours enter upon any premises occupied by or under the control of any telephone utility. The Commission, each commissioner and any employee of the Commission authorized to administer oaths may examine under oath any officer, agent or employee of such telephone utility in relation to the business and affairs of such telephone utility, but written record of the testimony or statement so given under oath shall be made and filed with the Commission. Any person other than a commissioner demanding the right to perform any act authorized by this section shall produce written authority from the Commission authenticated by its seal.