Unauthorised Debit Orders!!!!!!!

I have called Absa twice today to get contact details for the many debit orders going off my savings account. I have 5 different debit orders going off each month that I have no idea where they come. Most of them are R99. I don't use this account on a day to day basis so don't check it. In December some of the debit orders bounced to to insufficient funds which caused me to look why I had not funds available. When I saw the debit orders I queried them with the bank and they gave me some of the contact numbers - some don't work at all. I find this unacceptable that anyone can just start a debit order on my account - how did this happen and surely the bank should get your approval first? How am I supposed to reverse the debit orders of the ones I can't get contact details for???? Please advise????

Kind Regards, Tammy