If any insurance for which an amount is included in the contract or charge agreement is cancelled, any unearned insurance refund exceeding one dollar received or receivable by the holder or, if the amount included for insurance in the contract or charge agreement exceeds the premiums paid or payable by the holder, any unearned portion of the amount so included exceeding one dollar shall be credited on the final maturing installments of the contract except to the extent those amounts are applied toward payment for similar insurance protecting the interests of the buyer and the holder or either of them.