Incorrect Bill cannot be resolved after two weeks

During late 2015 I ordered an Explorer on the R899 decoder payment plan from DSTV which was delivered and installed and attached to my extraview decoder. In late November a second decoder was delivered in error. I notified DSTV and following numerous phonecalls DSTV finally understood and the explorer was collected by the courier for return to DSTV. My January bill was double what it usually is so i called DSTV to query. It turns out I have been billed incorrectly for the Explorer which was returned to DSTV - R899 on the decoder payment plan. I am also being billed the incorrect amount for the Explorer which is installed and operating, as this should be on the decoder payment plan but is not listed as such on DSTV's system. <br> I have now called four time, and each time the call centre agent agrees that the error is on their side but the DPP department must resolve it so they will call me. My first call was on 4th January, second on 8th January and third today and still no response or resolution - surely if a company sees an error on their system they should be able to resolve it timeously!