Hi Abinassn,
Do a Google search on 'Management and Human Resources' + 'New Route PhDs'. Typically, the New Route PhDs offer classes as part of the PhD programme. As far as I am aware, as a PhD student, you are welcome to sit in on classes taken by Masters/Undergrad students at your university, but if you are not taking the New Route PhD, these may not count towards your degree.
Best of luck!