S.C. Code Ann. § 58-17-2090

When any common carrier charges more than the legal rate of transportation applying to any goods, commodities, livestock, or any other kind of property, as shown by any rates fixed by law or by the tariffs filed with the Office of Regulatory Staff and approved by the Public Service Commission or, in the case of interstate transportation, by the Interstate Commerce Commission, as required by law, the consignee or owner and holder of a bill of lading, or the owner of any property transported, who may have paid the illegal charge has the right to recover in any court of competent jurisdiction the amount paid in excess of the legal rate applying to the property and the person shall not be defeated of a recovery on account of the fact that the payment may have been made voluntarily. But an action shall not be maintained hereunder until after thirty days from demand upon the common carrier for the repayment of the excess charges.