Telkom Debiting even after account is closed.

I closed my contract and paid R8200. According to Telkom the payment reflected on their side on 11 April. After 6 days later they come again and debit R5k and it bounces. They now refusing to pay me back my R130 that was charged by my bank for bounced debit order. My account was paid in full and closed, the number was even changed to prepaid. Why can’t they be responsible to pay for my bank charges if they come and debit while I don’t owe them? I want my money back!!!!!!!!!!!!!