The rates fixed or authorized by this Commission are to be regarded as maximum rates, which the railroads shall not exceed, except when specifically authorized by rule or written consent of this Commission. The railroads may adopt lower rates with the consent of the Commission, but if they do so for one shipper or person, they must, for like service, apply the same reduction of rates for all other persons and if they fix less freight rates from one station, they shall make a corresponding reduction of the same per cent, at all stations along the line of road, so as not to discriminate against any person or locality except as provided in 103-25.
S.C. Code Regs. § 103-26