I am paying for services but not getting them

I bought a DSTV decoder on 21/08/2015. I called the number on the box to get it installed. The lady I spoke to arranged to have someone come through on the same day to have it fitted. The technician arrived and installed everything. I noticed that the channels were not working via HDMI as it should have but rather via the AV screen, when I asked him why this was happening, I was told it will work once I have made the payment. The technician completed the installation and told me I need to call the call center and they will activate everything. He signed a few documents and gave it back to me. After I called the call center and activated the account for the Premium package, I noticed that not all of the channels were working. I had called back a few times since then and had gone through the process of rebooting the decoder and disconnecting and reconnecting and have still not been able to get coverage of more than 15 channels. It has now been decided that I need to get the technician to come back and sort this out however, DSTV are not able to give me the details or contact numbers for the tech. and I am now paying for something that I am not getting. This is unacceptable!!!