Unused Product

I just took over this GM parts department and have a ton of Wynn's product that the previous service " manager " had swapped in for some BG stuff. It doesn't sell AT ALL but local Wynns guy won't take it back or give any
" in store credit " I've got a part number list and am willing to sell below cost of course. Thanks
" in store credit " I've got a part number list and am willing to sell below cost of course. Thanks