Imagine going to get your car repaired, paying for it, and then finding out the work was never even done. With the help of insiders, an NBC affiliate uncovered an apparent scheme at stores that are part of a nationwide chain with 30 million customers a year.

To conduct the investigation, they wired two test cars with hidden cameras in places mechanics wouldn't find. Then, they drove one of the cars to a Jiffy Lube, to get an oil change.

They were charged for a new filter and the service advisor insisted he changed it. But he lied. Before taking the car in, the investigative team lowered the gas tank and marked the fuel filter with a big "four." After leaving that Jiffy Lube, they checked the fuel filter, and the original one with the "four" was still on the car.

"It's so easy to get away with, so why go through the trouble of doing it," a former Jiffy Lube employee told them.

When they took their test car to a second Jiffy Lube, a manager recommends a top of the line transmission flush. "How does that work?" the undercover producer asked. "We do it with the machine," the technician replies. A machine called T-Tech, which they're supposed to hook up to the transmission lines under the car, to suck out all the dirty fluid.

But the entire time the test car was being serviced, no one ever touched that machine, and the hidden camera shows no one ever touched the transmission lines underneath. They charged for the T-Tech service anyway.

It happened again at several other Jiffy Lube locations. In all, they got stiffed at five out of nine Jiffy Lube locations.

Click to watch the entire video segment.

Source: NBC4 in Los Angeles