Whenever I know I'm being paid wrong I bring it up with management. They usually tell me theres nothing they can do. Thats fine, theyre probably getting screwed by the company too.
Just keep working, keep doing overtime, and keep track of everything you are owed.
When you leave you can hit up the company for whats missing. They will drag it out and try to tire you out. Stick to the figure you know are correct. Dont drop anything or accept a deal. Threaten to take it further with the relevent governing bodies.
Most companies will pay you, hoping you'll just fuck off and that they wont have to make changes and pay everyone what theyre owed. Then most importantly, once youre paid, report the company so that everyone gets paid correctly.
This has worked for me everytime I've done it.