How do you get an employer to pay you for overtime hours already worked .overtime was taken away

Your question presents at least two issues and maybe more.  First, an employer who agrees to pay you a certain amount or on the basis of a certain formula, cannot change its mind after you have performed the work.  It can tell that for the next time you work the rate or the forumula has changed and if you do the future work you are deemed to have agreed to the change.  Second, the vast majority of employers (but not 100%) are required by federal law to pay overtime (1.5 times your regular hourly rate) for all hours in excess of 40 in a given workweek.  There are some exceptions to this reqirement if you are a manager, office administrater, or professional (engineer, accountant, lawyer) and you are paid a salary.  Assuming you are not "exempt" from the overtime rules, the first thing to understand is that the overtime kicks in only after you have worked 40 hours in a single week (not after more that 8 hours in a single day).  So your employer could make you work 4 10-hour days and send you home for the rest of the week and not owe any overtime.  Second, unless you are a public employee, the employer must pay the overtime, not just give you time off the next week or later.  Third, the employer cannot make you clock out an then work off the clock.  If the employer requires or permits you to work overtime or has knowledge that you work overtime hours and doesn't stop you it owes the overtime. So to address these questions you could contact the US Department of Labor, Wage and Hour Division.  There is an office in each of the big cities in Texas.  Dallas and Fort Worth share one which is located in Arlington.  They will accept your complaint, investigate and collect the unpaid overtime hours, however the process may take several months.  You can also contact a knowlegeable labor and employment lawyer in your area.  If the employer is failing to pay overtime to all or a large group of its employees, certain class action proceedings are available.  Either way federal law protects you from retaliation for filing complaints about unpaid overtime.  Good luck.