(2) When a retail installment contract provides for a service charge computed by the actuarial method:
(a) The retail installment contract may provide for any other charge, cost or fee allowed under ORS 83.010 to 83.190 and 83.820 to 83.895, in addition to the service charge.
(b) The amount to be disclosed as the service charge and used as the service charge component of the other amounts disclosed pursuant to ORS 83.010 to 83.190 and 83.820 to 83.895 shall be the amount of the service charge to be paid assuming all payments are made exactly as agreed.
(c) The refund credit provisions of ORS 83.130 shall not apply. [1983 c.432 §4]