Notwithstanding any regulation or order of the Public Utilities Regulatory Authority which permits the imposition of a late payment charge by a public service company on customer bills, the state and any political subdivision thereof: (1) Shall not be subject to such charge on any bill which accrued on or before June 5, 1975; and (2) shall not be subject to such charge on any bill which accrues after said date, for the first sixty days after the due date of such bill.