§ 102. Rates; discrimination; liability. Except as to terminal warehouses, show rooms and factories, such a corporation shall be a common carrier. Subject to regulation by the commissioner of transportation, such a corporation may make regulations and fix rates for each class of its business. Such corporation shall impartially serve all requiring its service within the locality described in its certificate of incorporation up to the maximum capacity of its plant and equipment. No receipt, certificate or order shall be made, issued or accepted by any such corporation for any commodity not actually in its possession.