Unresolved matter with regards to an increasing debt

This is with regard to the account that i have been paying. Its a Jet account that has been handed over to Nimble credit fund 1/Norman and Bisset co. after Edcon was closed.

So from between Dec 2020 and July 2021 I have been struggling to pay a required installment as i wasn't working,but i was able to make an arrangement of paying a minimum of R50 to avoid extra charges.

So I got a job in August 2021, then i asked them to send me an outstanding balance of which they did. I also told them that from August end I'll be able to pay a required installment of +R599, and i have been paying more than what was required since then.

The initial debt as of august 2021 was R4680,02 with the installment of R599. So every month end since August 2021 I have been paying an istallment of between R700 and R1000 (so far I've payed R4600).So according to me i should be left with R80,02 which I should pay at the end of January 2022 .

To my suprise when i check online(using the link given) the debt keeps increasing with a debt of R800+.I feel like I am being **********. I have also tried to call them to ask what is happening, why is the debt increasing when I pay what is required of me and on time.

Apparently I have to pay via debit order to avoid interests, but how when I pay before due date? And besides I am only told now of such;that debit order is 0% interests and any other payment method like pay@ is interest charged whether you pay accordingly(before due date and pay the required installment) or not.

Also when I was paying R50(when I was not working) the interest was a bit low as compared to now when i pay +R700, and this honestly I also don't understand and they have since said they will call me to resolve everything but they haven't.

Since I have given them a call in October 2021 they are no longer sending me statements, they are instead sending me letters to say I should do a stop-order. The last statement(s) they sent also are different from those of when I was paying installment of +R50, they are ***** as they don't show any interest fee as compared to then.