Early payment on account

My discovery account was handed over to SSDA Ref *** after i lost my job and there was an excess that i was still owing - i had made payment arrangements to pay monthly until the account was cleared. The fact that one is unemployed and has no form of income makes little difference to them and i borrow money to pay this account off. I pay latest by the end of the month or before depending when i get money, i contacted the office and spoke to Incconetia Sibande as i recieved an sms stating my account was not paid. I was told that i need to pay on the arranged date and not before or after as the system will see the payment not coming in on that date. Her attitude was terrible as she can not understand that i pay when i get money and after receving an e mail that payment was recieved and the system is updated why do i get a generated sms from the same system, The sms that i will have to pay for - i find it hard to believe that the system cant pick the payment was made before if it was updated. SSDA are quick to call for non payment and adding cost for call etc but their system cant be updated or over riden with actual information when payment is made.