
Quoting
Mr. Knowitall
"Annexures" is a term used in Australia to reference an appendix or attachment to a contract.
If you are telling us that you were employed under a contract that originally provided for your employer to voluntarily pay you overtime pay, even though you were properly classified as an exempt employee, but that upon proper notice the employer is telling you that prospectively your overtime pay will not be calculated at 1.5 times your 'computed hourly rate', they can do that. As an exempt employee they can also tell you that your base salary is all you get, no matter how many hours you work.