Mo. Rev. Stat. § 390.121
Whenever, after hearing, upon complaint or in an investigation on its own motion, the division shall be of the opinion that any individual or joint rate, fare or charge, demanded, charged or collected by any common carrier by motor vehicle or by any common carrier by motor vehicle in conjunction with any common carrier by railroad or express, for transportation; or any classification, rule, regulation or practice whatsoever of such carrier or carriers affecting such rate, fare or charge or the value of the service thereunder, is or will be unjust or unreasonable, unjustly discriminatory, unduly preferential or unduly prejudicial, it shall determine and prescribe the lawful rate, fare or charge or maximum or minimum, or maximum and minimum rates, fares or charges thereafter to be observed, or the lawful classifications, rules, regulations or practices thereafter to be made effective.
§ 390.121, RSMo