Woolworths demands 2 installments in 1 month

My installment in November was paid by the 27th. In dec my statement came through via mail on the 17th and I went into a store and made payment. This payment would generally have been paid by the 27th of December 2020, however since I had the statement, I decided to do the right thing and make payment. On the 18th of December 2020 I received an sms stating that Woolworths now wants another installment of R1023.08 By the 11th of January 2021. How is that possible when this should be paid by the 27th of January. 2021? I have mailed them and sent a message on fb but I received a message that I MUST MAKE PAYMENT BY 11 JANUARY 2021. Woolworths wants 2 installments for 1 month? No one must pay installments when they receive their statement as Woolworths penalizes you for paying and the greedy idiots want 2 installments!