I. A premium finance company shall not charge, contract for, receive, or collect an interest or discount charge other than as permitted by this chapter.
II. The interest or discount shall be agreed upon by the parties and shall be computed on the balance of the premiums due (after subtracting the down payment made by the insured in accordance with the premium finance agreement) from the effective date of the insurance policy for which the premiums are being advanced, up to and including the date when the final installment of the premium finance agreement is payable.
III. Notwithstanding the provisions of any premium finance agreement, any insured may repay the obligation in full at any time. If the insured voluntarily prepays, he shall receive a refund credit, which shall represent at least as great a proportion of the interest or discount as the sum of the periodic balances after the month in which prepayment is made bears to the sum of all periodic balances under the schedule of installments in the agreement. Where the amount of the refund credit is less than $1, no refund need be made.