Section 6
SEC. 6. All telephone lines and systems for the transmission of messages and signals owned, maintained, or operated by the grantee, its successors or assigns, shall De operated and maintained at all times in a satisfactory manner, so as to render an efficient and elective telephone service. It shall be the further duty of said grantee, its successors or assigns, whenever required to do so by the Public Service Commission, to modify, improve, and change such telephone system or systems, for the transmission of messages and signals by means of electricity in such manner and to such extent as the progress of science, and improvements in the method of electrical transmission of messages and signals may make reasonable and proper.