Except as provided in this section, no creditor shall modify the terms of any agreement with a consumer with respect to any outstanding obligation of the consumer, which results in an increase of the rate of the finance or other charges or an increase in the amount of an installment or periodic payment due, or which otherwise adversely affects the interest of the consumer. A modification agreed to by the parties which applies to obligations incurred by the consumer after the agreement for modification is permissible.
SDCL 54-3A-7