S.C. Code Ann. § 37-2-206

If a buyer owes an unpaid balance to a seller with respect to a consumer credit sale, refinancing, or consolidation, and becomes obligated on another consumer credit sale, refinancing, or consolidation with the same seller, the parties may agree to a consolidation resulting in a single schedule of payments pursuant to either of the following subsections: (1) The parties may agree to refinance the unpaid balance with respect to the previous sale pursuant to the provisions on refinancing (Section 37-2-205) and to consolidate the amount financed resulting from the refinancing by adding it to the amount financed with respect to the subsequent sale. The seller may contract for and receive a credit service charge based on the aggregate amount financed resulting from the consolidation at a rate not exceeding that permitted by the provisions on credit service charge for consumer credit sales (Section 37-2-201). (2) The parties may agree to consolidate by adding together the unpaid balances with respect to the two sales.