Someone living in your flat...

I was renting out my property in Reyno Ridge Witbank. An agent from direct sell properties got the key from my renting agent claiming she wanted to show the property to a possible tenant. She then made copies of the key, and rented out my property without informing me and even worse without paying me a cent. The person moved in and I happen to find this out half a month later when a new tenant, who paid a deposit and a months rent to me, wanted to move in, only to find someone living there already. I had to replace all the locks in the unit as a safety measure.