They haven't returned my deposit

We left the Eyethu House apartment, ***ned/managed by iThemba Properties) last year in November 29, 2017. We even called the building manager S'fiso as well as Obed to inform them that we're leaving.

In December 2017, we went to the iThemba offices in Marshalltown to enquire about our deposit and spoke to the manager who told us that we should write a letter with both parties signatures who owned the lease and email it. Which we did the same week. According to law, it states that they supposed to respond with 5-10 days, which they didn't. Again, in January 2018 we sent more emails, still no response. Eventually, we got a call on the 1st of February 2018 from the iThemba offices, from a female saying that we owe rent money from December 2017 to February 2018 and were threatened to being blacklisted. The same day, another call came in registered as PL Hardware + ********** 7792 on the directory, who they claimed to be lawyers of iThemba concerning outstanding payments from our side. We told the lady on the other line what actually happened (that we left in November 2017 and that iThemba Properties owe us the deposit money). We ended the call with the lady saying she'll talk to their clients and get back to us, which she hasn't. Instead we keep getting pestered by Alpha Collections every Saturday asking us to contact them. And when we do, they keep saying the same thing, "...they waiting for a response from iThemba, sorry about that".