Yes, it is illegal to not pay someone their new hourly wage after working a standard 40-hour workweek. The Fair Labor Standards Act mandates this by stating that all qualifying workers should receive one and a half times their regular rate for any hours worked beyond their set schedule. In some cases, employees may be exempt from these provisions due to their specific job duties or salary. Hiring an employment attorney can help provide clarity to any instances where an employer has denied overtime pay by investigating and determining if their behavior is just or illegal.