Week off rules. Different rules for Company pay-roll and Associate employee.

I am working in a Telecom industry, O&M department. As per company rules working hours should be 9:30am to 6:30pm with 30min break and Saturday and Sunday as week off, But only Sunday is allowed as week off for associate/ off-role employee. Is this leagal?
when I asked my Reporting Manager about this he replied "there are different rules for on role and off role employee. Off-role employee have only Sunday as week off". How could it possible that in a same organization different rules for on-role & off-role employees when the duty hours (9:30am to 6:30pm) is same for all?

There can be two rules for off roll employees and on roll employees. But there cannot be an employee working for more than 48 hours a week.

Ask for payment for over time, if your work span is more than 48 hours in 6 days of working than of asking for additional weekly off day.