S.D. Codified Laws § 49-31-3.3
The commission may, within ninety days after July 1, 1988, conclude an investigation into any or all of the telecommunications services listed in §§ 49-31-1.1, 49-31-1.2, and 49-31-1.3 to determine if any service is properly classified pursuant to the standards found in subdivisions 49-31-3.2(1) to (5), inclusive. The commission may, after notice and hearing, reclassify any service to conform the classification of the service to the evidence and the standards in § 49-31-3.2. The telecommunications company providing the service has the burden of proving the classification is appropriate. During this ninety-day period, any service subject to the investigation will remain under rate of return regulation. Upon expiration of the ninety-day period, reclassification of any service, even if hearings had commenced within the ninety days, will be pursuant to the provisions of § 49-31-3.4.
SDCL 49-31-3.3