Accounts

I made a payment of R520 on the 27th January 2020 for the installment due but Ackermans did not allocate it towards my account. I went to the store on Friday and then again Saturday as i wanted to purchase school shoes for my kids. i was told that i have no credit due, when we called to find out if my payment was allocated, i was told yes but my account was overdrawn!!! how the hell can this be possible??? as i pay my account every month and if i do purchase and the amount is higher then my available balance i always pay cash. How can my account be overdue for the exact amount of the payment i made, it does not make sense. how many other months i have paid for and this payments were never allocated... Ackermans is a *******... i thought i would keep this account for my kids but now i realize this is a big mistake!!!