Mont. Code Ann. § 33-18-606

If it is determined through the dispute resolution process set forth in the federal Fair Credit Reporting Act, 15 U.S.C. 1681i(a)(5), that the credit information of a current insured was incorrect or incomplete and if the insurer receives notice of that determination from either the consumer reporting agency or the insured, the insurer shall reunderwrite and rerate the consumer within 30 days of receiving the notice. After reunderwriting or rerating the insured, the insurer shall make any adjustments necessary consistent with its underwriting and rating guidelines. If an insurer determines that the insured has overpaid the premium, the insurer shall refund to the insured the amount of overpayment calculated back to the shorter of either the last 12 months of coverage or the actual policy period.