Damelin not paying money back

In December 2014 we decided to pay off our Damelin account in full. We then communicated this with Damelin and requested a paid up in full letter.. In April we noticed that Damelin was still taking money from a debt order every month since we had paid in full. Since then they have not refunded us our money back... After countless phone calls spending 100s of Rand worth of airtime to be transferred from one person to the next and then being cut off 90% of the time. My wife has been in contact with Tyrone L. Booysen that is the Team leader at Damelin that keeps on promising that he is attending to the matter but with no result... How can a company handle itself in this manor..?