I am working as a security guard, at the same site for 8 years. A new company has taken over the contract and is now

Customer: I am working as a security guard, at the same site for 8 years. A new company has taken over the contract and is now changing our roster we work 7 days a fortnight including one weekend. This makes our income a lot better than ordinary hours. However, it appears they want to bring in another back up guard and they will be rostering him on weekends. Do we have any say in our roster? thank you.
JA: Are you hourly or salaried? How many hours do you work each week?
Customer: Hourly we were working 84hours a fortnight with any hours over 76 paid as overtime on the last shift. We agreed to work 12 normal hours per day. With our initial company we did not have any overtime as the excess hour were deemed our normal roster as it helped our site.
JA: Where are you located? Overtime laws vary by state.
Customer: NSW
JA: Is there anything else the Lawyer should know before I connect you? Rest assured that they'll be able to help you.
Customer: Only that they have issued us with three contracts so far. The first was standard. The second we thought was to include the Clause 13.3c of the Security Award and that we would not be paid overtime we were all in agreeance. Then the first fortnight pay penalty (weekend) were missing from our wages. We contacted they said there was a miscommunication as we received a level increase which they kept saying remove the overtime. We never agued about the overtime we were concerned regarding the penalties. The third contract has now basically gone back to the first with the inclusion of clause 13.3c and a new probation.