Unauthorized debit

So I opened a cheque account with Absa which now am enquiring about unauthorized debit orders penalty fee and I was told that my account was on a minus for R7. 10 and they charged me R100 this is ridiculous am moving my banks moving to a cheaper account that doesn't over charge me for something also the employees can't explain to me Absa it's *** I wouldn't even recommend family members to use it that charges are high and the bank it's even useless am so unhappy because the call Centre Agent couldn't even explain that to me now I had to downdrade my account to a savings account.