Worst Payment Plan EVER

I make payment on my Ackermans Account like clock work every 27th or 28th of the month. 28th October 2017 i paid installment for October ( R445 ). With the plan to free up more funds for the festive period, I paid R2000 on the 3rd November 2017 for November installment and to cover December installment. With all my other accounts, MRP, edgars etc, I now do not need to pay November or December installments. I get an SMS from Ackermans asking for November payment. I call their call centre and am told that Ackermans does not work this way and i need to pay Every month. What BS is this?? So what was the point of me paying the R2000 then? My account payments according to me is now in the positive so Ackermans can go to hell for NOvember and December. I will only Be making my installment payment again in January. If thats a problem for ackermans, Then they can return my R2000 and i will use it to make monthly installments. Pathetic since i have been A good paying customer since i have this account.