Account debited without authorisation

I am really disappointed in FNB, firstly I complained about the **** debit orders for R99.99 that have been going off my account, I was told a consultant will call me back and to date no one has called me back. Today my savings account was debited by FNB without my authorization for the amount I owe on my smart device. The arrears were sent to the lawyers who contacted me to make a payment on the account. I have never given FNB authorization to debit my savings account with the amount owed, in actual fact the smart device account was linked to my cheque account. This to me constitutes as theft where banks can just go into people's accounts and debit without permission. I need the amount credited back to my account.