Upon complaint in writing that any rate, classification, regulation or practice charged, made or observed by any public utility is unjust, inaccurate, or improper, to the prejudice of the complainant, the commission shall proceed to investigate the matter. The procedure to be followed in all such cases shall be prescribed by rule of the commission: Provided, however, That in all cases reasonable notice shall be given to the parties concerned as to the time and place of hearing. An investigation of any such complaint, and the formal hearing thereon, if such is deemed necessary, may be held at any place within the state and by any member or members of the commission, or by any duly authorized representative thereof. Witnesses may be summoned and the production of books, and records before the commission, or the member, or any duly authorized representative thereof conducting the hearing, may be required. Any witness summoned to appear or to produce papers at any such hearing, who neglects or refuses so to do shall be deemed guilty of a contempt. It shall be competent for the commission in any such case to make application to any circuit court of the state setting forth the facts of the matter. Thereupon said court shall have the same power and authority to punish for the contempt and to compel obedience to the subpoena or order of the commission as though such person were in contempt of such court or had neglected or refused to obey its lawful order or process. The taking of testimony at such hearing shall be governed by the rules of the commission: Provided, That at the request of either party a record of such testimony shall be taken and preserved. Upon the completion of any such hearing, the commission shall have authority to make an order or decree dismissing the complaint or directing that the rate, charge, practice or other matter complained of, shall be removed, modified or altered, as the commission deems just, equitable and in accordance with the rights of the parties concerned. For attending on any such hearing, any witness summoned by the commission shall be entitled to the same fees as are, or may be, provided by law for attending the circuit court in any civil matter or proceedings, which said fees shall be paid out of the general fund in the treasury of the state. All claims for such fees shall be approved by the secretary, or by some member of the commission, and shall be audited and allowed by the board of state auditors.