DSTV cancelled service still being charged

Have cancelled my subscription in Feb 2019 with DSTV - all paid in full up front, nothing in arrears - they have since tried 7 times to take money from my bank account after I cancelled EVERYTHING - today a debt collector phones me for the R127...I have called them 7 time since I cancelled the subscription to inquire what is going on at DSTV and why they say I owe anything. Before I know it I will be blacklisted for R127. Someone are not able to press the right button. DSTV what else must be done for your staff to follow through simple task?? They now telling me that its was an arrears amount from 3 years ago. Not possible - all there accounts are billed up front for the month and payable. I have had it and no one is able to assist - there reply being pay the money. I do not owe it I will not pay it. DSTV is a bully and will do what ever and rune people's credit record with no little or no explanation. I know for a fact I don't owe a cent it never appears on any statement, was always paid up in full with them.