(a) A pawnbroker may contract for and receive a pawnshop charge in lieu of interest or other charges for all services, expenses, costs, and losses of every nature but not to exceed 25 percent of the principal amount, per month, advanced in the pawn transaction.
(b) Any interest, charge, or fees contracted for or received, directly or indirectly, in excess of the amount permitted under subsection (a) shall be uncollectible and the pawn transaction shall be void. The pawnshop charge allowed under subsection (a) shall be deemed earned, due, and owing as of the date of the pawn transaction and a like sum shall be deemed earned, due, and owing on the same day of the succeeding month.