[§271G-20]  Collection of rates and charges.  No water carrier shall deliver or relinquish possession at destination of any freight transported by it until all tariff rates and charges thereon have been paid if such delivery or relinquishment without payment of all such rates and charges has been prohibited or restricted by rules and regulations of the commission, and if so prohibited and restricted, then delivery or relinquishment shall be made only under such rules and regulations as the public utilities commission may from time to time prescribe to govern the settlement of all the rates and charges, including rules and regulations for weekly or monthly settlement, and to prevent unjust discrimination or undue preference or prejudice; provided that this section shall not be construed to prohibit any carrier from extending credit in connection with rates and charges on freight transported for the United States, for any department, bureau, or agency thereof, or for any state or political subdivision thereof. [L 1974, c 94, pt of §1]