DSTV Overcharging and Unduly Enriched for 3 years of incorrect subs!

We realised on 19 March this year (2019) DSTV were overcharging us by one whole premium and had been since March 2016. They have been unduly enriched to the tune of over R30 000 (plus interest its closer to 40K). When we asked them as to why they had been overcharging us they removed the third charge (as we have two premium accounts) which we feel was an acknowledgement of their liability. However they refuse to refund us that money. In fact they fail to even look at the facts and understand the case- passing us between six or seven different people all of whom had no idea how to address this problem. Today they simply flatly deny any refund is due. The issue was escalated to the Office of the CEO , Legal and Regulatory Affairs but in all correspondence they fail to even see the issue as they do not look prior to April 2019- they say we get what we are paying for. We do NOW since we corrected them. BUT where is the money for the service we paid for and never received for THREE YEARS!!! BE WARNED DONT RELY ON THEIR SYSTEMS AND ADMIN. Download your statements from their website monthly and track your accounts carefully. Our error was that we trusted our service was always the same (as it had been for nearly 15 years) and the debit order was correct.