S.C. Code § 38-73-1105
The definition of "underinsured motor vehicle" contained in Section 38-77-30(15) may not be used by an insurer unless the insurer reduces his rate for underinsured motorist coverage by an amount determined appropriate by the director or his designee and refunds any such premium that the director or his designee determines is necessary to correspond with the new definition. An insurer may not use the definition in its settlement negotiations unless the insurer has filed and the director or his designee has approved an endorsement to its contract. If an insurer uses the new definition in its negotiations with a person before having the contract endorsed it is an unfair claims practice and, in addition, is bad faith entitling the injured person to reasonable attorney fees, punitive damages, and all actual damages.
S.C. Code § 38-73-1105