Not as agreed

I have requested a 6 months reduced payment for 6 months on both my home loan accounts and paid the reduced amount each month. At some stage there app did not work and I could not see how much to pay on one account. I bought this under the attention numerous times. As I could not see what to pay I had too guess. Now after 6 months I requested that both accounts be extended by 6 months to clear any arrears. I have been send forms to fill in, which I did. It has been approved as far as I know. Now one account is in arrears with over R6000 which cannot be as I paid the amount agreed each month. This was not the account that did not work on the app, so the full amount was paid each month, it cannot be in arrears, So is both accounts extended by 6 months as agreed or not. If not it has to be fixed to as not be in arrears. Also I have been advised to change the due date of the account the same day I pay. Now I have informed this cannot be done as it is in arrears. Also note that no debit order must be in place as the installment is taken from my salary and paid directly by my employer to ABSA and cannot be paid twice in a month. Please fix this mess.