VODACOM BAD SERVICE

I cancelled all vodacom contracts more than a year ago. They kept the debitorder going untill I stopped it. I sent them many letters regarding the cancellation. No feedback received. Now they gave the R600 that they claim I owe them to a debt collector, who is harassing me morning noon and night. After one of these phone calls they advised me to go and do an affidavit regarding the cancellation. I did that. The debt collectors have not sent me their email address yet after many requests. I sent the affidavit to vodacom, still no feedback. How do I get rid of VODACOM without going to court?