S.D. Codified Laws § 49-11-8
If a state law, a county or municipal order, resolution, or ordinance, or a Public Utilities Commission order or rule, fixing the rates for any service rendered by a public utility or public service corporation, is enjoined pending litigation by any court for any cause, and it is finally determined in such litigation that the rate litigated was lawful and valid, the common carrier, public utility, or public service corporation shall refund immediately to the person entitled thereto any rate or charge exacted or collected in excess of the amount authorized by such law, order, resolution, or ordinance.
A violation of this section or a Public Utilities Commission order issued pursuant to this section by a common carrier, public service corporation, or other public utility subject to this title or by an officer, agent, or employee of such companies is a Class 2 misdemeanor.
SDCL 49-11-8