S.D. Codified Laws § 49-31-89
The telecommunications company of any subscriber may not be changed without the telecommunications service subscriber's authorization. The telecommunications service subscriber's authorization shall be evidenced either by a written authorization signed by the subscriber or by the use of an independent third-party verification company which complies with the provisions of §§ 49-31-90 and 49-31-91, or by any other means authorized by the commission. Products or services may not be listed on a subscriber's bill unless authorized by the subscriber. The commission may promulgate rules pursuant to chapter 1-26 concerning procedures, requirements, and standards for changing a subscriber's telecommunications company and for listing products and services on a subscriber's bill.
SDCL 49-31-89