(a) On request of the retail buyer, the holder of a retail installment contract may:
(1) amend the contract to renew, restate, or reschedule the unpaid balance of the contract; and
(2) collect an amount computed on the principal balance of the amended contract for the term of the amended contract at the applicable rate under § 345.055, 345.056, 345.057, or 345.058.
(b) The principal balance of the amended contract is computed by:
(1) adding:
(A) the amount of the unpaid balance on the date of the amendment;
(B) the cost of insurance;
(C) the amount of each additional necessary official fee; and
(D) the amount of each accrued delinquency charge; and
(2) subtracting from the total computed under Subdivision (1) an amount equal to the minimum refund credit that would be required under § 345.075 or 345.076 for prepayment in full on the date of the amendment.