DISGUSTED CLIENT COMPLAINT!!

This is by far the worst property management I`ve ever dealt with and I'm soooo disgusted!!! Their level of poor service and incompetency is out of this world. Moved in one of their flats at Jabulani Ekhaya complex on the 01/10/2017 and it was a 12months contract. 01 October 2018 I paid my rent as usual and also submitted a notice that me and my family will be moving out end of the month, which happened accordingly. On the 01 November 2018 I was sent a statement showing a R0.00 indicating that everything has been actioned and closed accordingly. However...To my surprise, about 4-5 months later I got a call from someone at IHS who said theres an outstanding amount reflecting on my profile...I then addressed this with him, sent him all the proof that I don't owe them anything...He then advised that they will update the system accordingly and close the account. They went quiet from then and I was under an impression that all is well. Now without any further communication from them...5 months later, I am sent a letter of demand from their Attorneys tell me that I have 5days to settle the outstanding amount of R4563.17 which I don't even know where's it coming from. I called the IHS offices a thousand times in order to get this sorted and I was told that "The only person that can help me is on leave and no one else can assist me".....WHAT TYPE OF NONSENSE IS THAT!!!! Their damn statements clearly indicate that they never stopped billing me even after I had vacated their premises on 31/10/2018...The outstanding amount is the November bill and I was no longer staying there...I even saw that new tenants moved in a day after we left the flat so what the **** is this outstanding about!!!!??? Such appalling incompetency!! Now their lawyer are threatening to blacklist me!! There wasn't sufficient communication for the matter to be assessed and resolved properly and now yall coming with Blacklisting threats...You gotta be joking. The same way yall gona do that, yall will do it in reverse and fix it...I DEMAND THAT SOMEONE COMPETENT CALLS ME AND FIX THIS MESS!!