"You are on notice to pay me $X. Should you not pay me before Christmas I will likely seek legal advice, and that is in neither of our interests."
I agree sham contracting is a possibility, but at a practical level you may lose your job if you seek to enforce your rights as an employee. What is more important to you - working (albeit temporarily till you find alternative work)? or being paid according to the award?
Suggest you keep working till you find alternative employment then go after what is owed.