Failure to collect rent efficiently

I have a unit in Villa Victoria complex in Boksburg. CSI Rentals manage the rental on my behalf. Things were fine in the last two years but towards the end of 2015 the collection became inefficient. My worry is that over R8000 is being owed by tenants although this agency takes the monthly management fee from me. The other issue is that I have raised this issue three times via e-mail but they purposely ignore my e-mails but they respond if we discuss other issues but settlement of this money. <br> <br> Phone numbers are not showing in their e-mails anymore.<br> <br> I'm frustrated because the shortfall is increasing badly.