1If the sales finance company discovers that, as a result of an inadvertent clerical error or some other unintentional mistake the finance charge to a buyer is in excess of the amount permitted, or that any other charges in the contract are excessive, it shall immediately notify the buyer in writing of such overcharge. The overcharge, plus any finance charge that may have been assessed thereon, shall be credited to the account balance, and the buyer shall be notified in writing of any reduction of contractual payments. Contracts paid in full containing excessive charges which were not previously given credit should be corrected by making a refund to the buyer.
