S.C. Code Ann. § 58-9-720

The commission may ascertain and fix just and reasonable classifications, regulations, practices, or service to be furnished, imposed, observed, and followed by any or all telephone utilities, prescribe reasonable regulations for the examination and testing of such service and for the measurement thereof, establish or approve reasonable rules, regulations, specifications, and standards and provide for the examination and testing of any and all appliances used for the service of any telephone utility.