S.C. Code Regs. § § 103-733
If it is found that a utility has directly or indirectly, by any device whatsoever, demanded, charged, collected or received from any customer a greater or lesser compensation for any service rendered or to be rendered by such utility than that prescribed in the approved rate schedules of such utility, then filed in the manner provided in Title 58 of the South Carolina Code of Laws; or if it is found that any customer has received or accepted any service from a utility for a compensation greater or lesser than that prescribed in such schedules; or if, for any reason, billing error has resulted in a greater or lesser charge than that incurred by the customer for the actual service rendered, then the method of adjustment for such overcharge or undercharge shall be as provided by the following:
S.C. Code Regs. § 103-733