Bad Service

I have 2 decoders with Dstv (Primary & Xtra View). I had problems for the past month with my two decoders. I phoned in the call centre and they cannot assist, I used more than 2 hours of my cellphone to sort out my errors. I went into the service centre on 4 occasions in March 2015 and they changed the decoders 4 times. I told them there is a problem with the refurbished decoders as it gives various types of error messages. Every time when they change the decoders, a different error comes up. I gave in my new decoders for these faulty products. I cannot seem to get hold of any manager and the contact numbers they provided is just ringing. I logged my complaint via email to the manager and I had no response. This is bad service and they cannot seem to resolve the issue.