False maintenance report, ******** people their money and threaten to blacklist

I rented at Windmill Park Estate for period of 12 months. They did their inspection when I moved out and a new tenant moved in immediately the day I moved out. Two months later they send me an invoice together with maintenance report (which does not correspond with their findings during their outgoing inspection report) together with a threat to blacklist me. Their findings were mostly dirty walls and loose door handles but according to their invoice, they have actually replaced the stove with a new one, installed a new kitchen unit, all this at my expense. Now they say I owe them R8500 on top of the deposit paid.