Outstanding payment

I was retrenched since 2017 momentum paid some of my provident same year then there was outstanding money that was supposed to paid as well,i spend 2years calling them requesting the money they end up paying half of the remaining amount last year November this year i start calling them from January even going to their offices whenever i ask they promise to pay me after 14days ,then they don't, last past 2 weeks i ask for statement they promise to send it but they fail I don't know why they kept the money with them since am no longer working for that company.