NUDEBT ****

I just discovered Nudebt has been deducting R189 for the past 3 months from my account *******ly without my permission . I did not know who they are until i went to enquire at the bank and when i call them the answering machine keeps saying they have high call volumes. I do not have any unpaid debt and i have never allowed Nudebt to debit my account and where did they get my account details and who approved the debit order?