False identity by ACU

I received a call from their agent claiming to be of NCR and want to help negotiate better interest on my home loans since there was an interest hike. I have confirmed with them throughout the call that they are not placing me under debt review and I was assured it's not debt review. I was shocked to receive a debicheck mandate from a bank I didn't even use, they got hold of my banking details from me when they requested that I send them my proof of acc to serve as proof of residence. When I made contact with the agent to find out what was going on, I was blocked and I got hold of their customer care which was where I learned that I needed to pay R6000 for the status to be removed I refused, I then later received a call which I was told I owe them R21000 or the status flag will remain on my name. NCR was consulted to notify them of the matter, answered all their questions and provided the requested information from me to them. The case was allocated to Motumiseng Tshimange, the lady plainly ignores my emails. Please help