Should I be getting paid for overtime?

I just started working through an agency at a Verizon packaging center where most employees are employed by New Breed Logistics. The job is simple all we do is look for the merchandise an order requires, make sure it is correct, put it in a box and send it down the line. Yesterday I worked the graveyard shift from 8pm-7am. When I talked to the agency they said overtime is paid after 40hrs of work, but I thought that anytime you work more than 8hrs in a day it is suppose to be overtime pay...is this correct?