Debit orders still going through months after I've cancelled!!!

Telkom, oh Telkom, why are you still debiting my account, every time with a different reference number, months after I cancelled all my services. You are quick to sell but oooohhhh soooo sssssllllllooooowwwww to cancel your terrible services. Please sort it out. I've had enough of all the excuses. I have been trying, for months, to get you to tell me what account it is that is still active and eating away at my hard earned money, and you can't even give me an account nr.