My account should be closed

I missed two payments with Telkom and I got penalized for the terms of my contract ,they cancelled everything and I ended up owing 9371 and it got handed over to Nu debt which came up to 10494,managed to pay that entire amount within two months.Got my paid up letter from Nu Debt,now when I call in to Telkom I get told my account is still active,my account is in credit they owe me money.Had I not called in Telkom would have continued to debit my account after they had used the money they owe to me.I paid everything ,this phone belongs to me,those devices belong to me.I need someone who’s going to resolve my issue and get that credited back to me.My lines are still suspended and they had the nerve of wanting to bill an inactive account ,**********s!