They trying to **** me and not gonna win!

These guys starting from 2 months back have suddenly been sending me statements that I owe them roughly R100, now every month they busy adding roughly R35 interest to this balance. I finished paying them years ago roughly around 2009, then they were silent until 2 months ago. What kind of a **** is this? I'm not paying a cent to this and good luck to them on trying to garnish me. ***