Dump working environment and lack of support for their casual staff

My little sister was a casual worker at this company, got her phones and the other colleagues ******. The permanent workers started isolating her and bullying her in the presence of the manager, these people where treating her unfairly and told the Centre manager that she stole the phones who came to accuse her. She now being told she had no prove. Also what about the manager who didn't take the liberty to report theft at work? . She laid a complaint and she was told that she should have laid a complaint with the manager. How do you lay a complaint to a person who is also enabling the culprits?? Shame on you!!!!