Mistreatment of black employees

I have worked for Mamba Control Centre for almost a year. The black employees are always mistreated than the whites. The control centre manager Roman and supervisor Wimpie are always shouting at black employees. Many including myself have written our complaints to the company but nothing has been done about it...... a result many have resigned because of the mistreatment. The mistreatment even goes to the black manager. His views are never considered. The treatment of black employees in the CC is bad we just work because we have to provide for our families. Senior management treats everyone equal but junior management treats black employees like she......t