Section 12. A. When any payment is made on account of any retail installment sale agreement, the person receiving such payment shall, if the payment is made in cash, give the buyer a complete written receipt therefor. If the buyer specifies that the payment is made on one of several obligations, the receipt shall so state.
B. Any person may purchase a retail installment sale agreement from a seller or holder on such terms and conditions and for such price as may be mutually agreed upon. Unless written notice has been given to the buyer of actual or intended assignment of a retail installment sale agreement, the buyer may pay or tender any amount due thereunder or give any notice required or permitted by the agreement, to the last known holder of the agreement and such payment, tender or notice shall be binding upon any subsequent holder as fully as if made to him.