Prosperitas making up amounts and claims, no response

After settling my account in May of 2022, I received another bill for R7100.00 in schoolfees debt. I settled Prosperitas and I have been paying my schoolfees every SINGLE month. They are not threatening to list me on ITC despite receiving settlement letters. I want answers but have not received any call backs or response on my e-mails. I smell a rat between Prosperitas and the school in question. I demand answers and a solution as I refuse to pay R7100 that has suddenly appeared out of thin air.