Account debited

I found my account debited with R119.99 when I phoned Nedbank to inquire about this debit order they informed me that Stratcol took the money from my account. <br> I phoned Stratcol spoke to a lady called Jane and she said that Prestige authorised them to Debit my account I phoned Prestige Group of Recruitment and training ans spoke to a Nisa . She said that she will get her manager to phone me back. I insisted that she put me through to their accounts department and she just kept on saying she will get her manager to phone me back. <br> <br> This all happened today. I would like to know how they got a hold of my bank account number and how does the bank authorize debit orders without signatures... what is going on here?