***** Accounting from Wesbank???

I need to understand how Wesbank works out it arrears amounts. After making my monthly payment for May, on the 27th, Wesbank then immediately loaded my next installment amount (due in June), however, I then started receiving calls from lawyers wanting to collect from me on the basis that I am in arrears for 3.35 months. When I look at my statement, I noticed the fact above; that they are calling to collect from me an arrears amount which is inflated by my June installment. My monthly payment date is on the 27th, and I have paid every month without fail. In cases where I was short, I paid no less than 93% of the installment amount. Therefore, I am unable to reconcile the fact that I would be in arrears by an amount up to 3x my monthly installment, and, in any event, why is Wesbank quoting my June installment as part of my arrears?????

Acc: ********** 2547

After speaking to the lawyers whom the case was referred to, they claim to not know how Wesbank calculates the amounts, but "are only hired to collect the quoted amount from me and want to take possession of the car until such amounts are settled".

As a matter of fact, I have 3 accounts with Wesbank which are up to date, their treatment in this regard has been unfortunate, and I believe that my relationship with the bank must come to an end as soon as I am able to settle all 3.