With respect to policies issued and certificates delivered after the effective date of these sections:(1) the refund of an unearned amount paid by or charged to a debtor for credit life insurance, or for credit accident and health insurance, on which charges to the debtor are payable by other than a single sum must not be less than the pro rata gross unearned amount charged;(2) the refund of an unearned amount paid by or charged to a debtor for credit life insurance, or for credit accident and health insurance, on which the insurance charges to the debtor are paid in a single sum must be computed by the rule of anticipation, as defined in §3.5002 of this title (relating to Definitions), or by another method which produces a substantially equal amount and is approved by the commissioner of insurance. This paragraph shall not be interpreted to preclude refunds for credit accident and health insurance to be computed by the mean of the gross unearned premium calculated by the "sum of the digits" (rule of 78) and the pro rata method.