I need my money ,I worked for it,it was supposed to be payed onthe 25 of August still nothing

I worked for Nurture Health Alberton for 2 and a half months and the Operating manager was bad that I had to resign but I work overtime for 4 days and they don't wanna pay me,they say when you resigned you loose your overtime money is that tru?They owe me 4 days .....36 night duty and 9 hours day duty.Nurture Health Alberton in Medimix building......My Manager name is Nathasha Moodley they owe me 4days that I have worked.......Hr people advise if it is true