69-12-502. Prohibition on deviation from rate schedules. It is unlawful for any Class A motor carrier to charge, demand, receive, or collect any greater or less rate, charge, or fare than that fixed by the commission for the transportation service provided. When maximum or minimum rates have been established for any service provided by any Class C motor carrier, it shall likewise be unlawful for the carrier to charge, demand, receive, or collect any greater compensation or rate than that established for the service by any applicable maximum rate or any less compensation or rate than that established by any applicable minimum rate. It shall also be unlawful for any Class A motor carrier or any Class C motor carrier subject to maximum or minimum rates to refund or remit, in any manner or by any device, any portion of the rates, fares, and charges required to be collected under the schedule of the Class A carrier on file with the commission or under the maximum or minimum rates established by the commission for the Class C carrier.