Can an employer manipulate your hours and add hours to a person working piece rate causing their rate to drop below the previously earned rate?

Employees paid on a piece-rate basis are not exempt from the various requirements of the Fair Labor Standards Act ("Act"), including minimum wage and overtime.  Piece¿rate is not a new or novel compensation technique; however, in recent years, the U.S. Department of Labor has dedicated substantial resources to investigating, penalizing, and prosecuting employers who misuse the piece¿rate system.  Even under a piece¿rate compensation scheme, employers must pay employees at least the applicable minimum wage for each hour of work (currently, $7.25 per hour).  This does not mean that employers are required to pay a certain rate per piece; rather, employers must ensure that at the conclusion of each workweek, all nonexempt employees have received at least $7.25 for each hour of work performed during the workweek.  It might be that the amount you earned at the piece rate was not sufficient to pay you at minimum wage for those hours and the employer had to adjust your pay so that you received at least minimum wage for that work week.  I don't think I have quite enough information to assess exactly what happened and whether you were paid correctly.   Now if you're saying that you worked over 40 hours that week between production and in-direct time, you are entitled to overtime.  Under the Act, irrespective of whether the employee is paid hourly or on a piece¿rate basis, the employer must pay the employee one and one¿half times the employee's regular rate of pay for all hours worked in excess of 40 hours in a workweek. Again, I'm not sure of the facts.  Sorry I can't be more specific.