Disgusted by Telkom Jubilee Mall(Temba)

I bought a wifi ****le at Temba, Jubilee mall Telkom, before then i explained to the guy by the name of Kenny what i needed to do with the ****le to connect DVR and he insisted that the one he gave me it will work, and i bought the thing with R1100.00 later to find out that it does not work, and i went back to exchange or refund so that i can get the correct modem but they refused to take it back that their policy it does not allow, surprisingly terms and conditions not not stated on the Invoice. Can someone help with this Please.