Billing issue

I have requested DSTV to switch off my service due to budget problems. They did not switch off my service and only switched it off two weeks later. After some time I reactivated my service, but now DSTV is holding me responsible for the 2 weeks of service.How is this my responsibility as I can not switch off the DSTV service/ signal from my side. Every now and again they suspend my service due to the outstanding amount and I have to spend 30min to 40mins on the phone to have my service switched on. I have requested them to listen to the phone call in which I have told the agent to switch off my service. When I ask them to call me back they say they cant. How can you sell a service and when a long time client, approximately 12 years, request a call back refuse to call him as your lines don't allow it. In my opinion you must make a plan to keep your old clients happy. This past month since the 10th until today I have spent approximately 2,5hrs on the phone with them trying to resolve their mistake. I have to pay my phone bill as well as their subscription. I guess this is what you get when a company has the monopoly in a country.