Section 9. Every public service corporation engaged in the business of transmitting messages for profit shall receive and transmit, without delay or discrimination, any messages delivered to it by any other public service corporation engaged in the business of transmitting messages for profit, and shall, with its lines, make physical connection with the lines of any public service corporation engaged in the business of transmitting messages for profit, under such rules and regulations as shall be prescribed by the corporation commission, or by law; Provided, that such public service corporations shall deliver messages to other such corporations, without delay or discrimination, under such rules and regulations as shall be prescribed by the corporation commission, or by law.