1999 Chevy Malibu Turn Signals, Brake Lights

I have done auto work for several years and have never seen this before. When I use my turn signals the back up lights blink and when Im in reverse the blinkers light up instead. I assumed that the lighting wires and bulbs were put in the wrong place on the tail light housing but when I looked I saw that you cant just switch the bulbs around, its one big manifold type hookup that a wireing harness goes into and all the bulbs are in a fixed location. I inspected the wires though the trunk and didnt see any cuts or splices in the wireing from any previous owners. I bought this car from a buy here pay here car lot, There just dumb hillbillys who don't know anything but how to take a payment.