Every employer has a responsibility to make sure it follows rules and regulations when dealing with the people it employs. As an employee you should be aware of your responsibilities as well as your rights.
Problems with Pay
If your employer witholds any of your pay it's called a deduction of wages. Find out when this is allowed and when it isn't and what to do here.
If you think you've been treated badly because of who you are, then this may be discrimination. Find out if it is and what to do about it here
Problems at work
Read about negotiating with your employer here
If you want to make a formal grievance read about it here