Dstv overcharging clients and getting no explanation as to y.

These *****s have debited me for R735, when my subscription is R510. I have called their call Centre, hung on for 45min as usual, go no help, I was told I was in arrears, God only knows how's that possible when u pay upfront for their pathetic service. This problem was been escalated multiple times but still no reply. I complained last week on help Peter, but never got a call either. I called the call Centre again on Thursday and was told they will refund me, which was a bunch of lies. How can I cancel this service being a pricelock client?