Unpaid Overtime

I'm a newly regularized employee, upon regularization my employer gave me an increase making my salary 19000/month. But they insisted I cannot claim overtime pay anymore since I am now in a supervisory position. I only have 1 year experience prior to joining this company and currently, I have no subordinates in our company. So I cant see the reason why am I in a supervisory position.... I only perform internal audit and some financial reporting functions.

How can I tell if I am really in a supervisory position?? Because I think they are only using that "supervisory" as an excuse not to give overtime pay.

Im not the only employee in this kind of situation in our company.

Supervisory employees are those who, in the interest of the employer, effectively recommend such managerial actions if the exercise of such authority is not merely routinary or clerical in nature but requires the use of independent judgment.