Mistreated of black employees

I worked at Mamba for almost two years.. the control centre is not a place to work. The controllers are never appericeted. There is a manager his name is Roman, he short at employees threatening us....Wimpie the supervisor always shouting and insulting us. Many including myself have written our complaints but nothing is done about it. A black employee is always mistreated than the whites. Alot of employees have resigned because of the treatment.