All rates, fares and charges made by any common carrier by motor vehicle shall be just and reasonable, and shall not be unlawfully discriminatory, prejudicial nor preferential. No such carrier shall charge, demand, collect, or receive a greater or less or different remuneration for the transportation of passengers or property, or for any service in connection therewith, than the rates, fares, and charges which have been legally established and filed with the commission; nor shall any such carrier refund, remit, discount or rebate in any manner or by any device any portion of the rates, fares, and charges required to be collected by the tariffs on file with or ordered by the commission.
W. Va. Code § 24A-2-4