Arrears charged even when account is up to date

On the 04th March 2016 I called Toyota Financial Services to get the correct amount due. Consultant Qondeni at TFS told me that the amount is R11632.21. I paid R11632.21 on the 4th March 2016, the statement acknowledges my payment. The problem is my statement of 18 March 2016 states that I still have arrears amounts. I had this issue since October 2015, I've sent several emails and made several phone calls to enquire but no one helped. Up until today I haven't got a clue why I am continuously charged arrears even after I pay the amount due. Does this mean my account will never be up to date since arrears keep on appearing even after I pay the amount due? When I pay the amount due on the 4th March 2016 the consultant assured me that my end of March statement will only have the installment due and R0.00 Arrears since the account is now up to date. Unfortunately, it's not the case. Can someone explain how TFS calculate these arrears? A Consultant gave me a formula (Arrears * days that you are in arrears * rate that you signed/Divide 365 days). My answer (R0 Arrears * 0 days in arrears * the rate I signed/366 days) equal to R0.00 Arrears.