Dstv not seeing to Customers issues.

Dstv is a pain. From December 2017 I'm struggling with them to pay back the credit on my account its ridiculous. I keep phoning every month but no success. Then on the other hand i get billed incorrectly every month from March 2018. Every time they promise me it will be fixed but it stays the same for the last 6 months now. Its frustrating I get told that its the system who calculate automatically but someone needs to put the information there. I'm fed-up looking for answers.