Exorbitant Installment of R572 on a balance of R1,706

According to my latest statement emailed to me end of June 2018, my balance due on my Jet/Edgards account (payable over 20 months) stands at R1,706.91. In addition, I haven't made use of this account for over a year (if not more) as I just want to get this paid and cancel this account due to the high monthly installment amount of R572.07 per month. Initially I thought this installment amount must be a calculating error on Edcon's side, but then called in after getting demand text messages almost daily to pay.

After going from pillar to post I was told that I was under administration which I know for a fact I am NOT. I called the Credit Bureau who confirmed that I have never been under administration or debt review and have a clear credit record and they even emailed me my report as proof.

I emailed this to Edcon and followed it up with more numerous phone calls, going from pillar to post and eventually after a few weeks was told that Edcon agree that I was not placed under administration, nor debt review and that they would review my installment amount. Eventually another week or so later, after sending more follow-up emails, I received a call from Edcon to tell my that my new amount due was under R100, yet I paid them R200.

Lo and behold! On 16 July 2018 I received a statement from Jet reflecting my R200 payment, but my installment amount IS STILL R572.07, BUT MY BALANCE DUE IS R1,706.91. CAN A MANAGER (WHO KNOWS HIS @SS FROM HIS ELBOW) PLEASE CONTACT ME BEFORE I GO OFF MY HEAD!!!!!!!!!!!!!!!!!!!!!!!!!!!