SHOCKING - Making me pay for the same decoder for the second time

A couple of months back I finisihed paying for my DSTV decoder that I had obtained through OnAir TV . At around the same time I started receiving messages and calls to 'upgrade' which I dully did. After receiving my decoder and getting my usual installer to assist me with installing, he told me that you had sent me exactly the same decoder as I already had. Not sure where 'upgrade' comes in. I have now been trying to get this returned for a few months and they are refusing to take it back - not even being able to give me the name of the CEO so I can contact them directly. I am also being threatened with being listed for non payment - after having stopped my debit order due to the reticence of not having to pay for another decoder - the same as I already had. I have been promised call backs relating to my query and eventually after still receiving threats around listing me for non payment I called again today. Basically telling me tough - i just need to keep it and pay for it. This is just such bad business practice and this together with poor dealing of the matter. I would advise never to deal with OnAirTv EVER