Unauthorised debits

I am really angry at FNB at this stage.I have been with them as long as I remember,but they such a let down.As bank how do you not know if your client is been ****** ,why as a bank do not sent a confirmation of debit ,to ask if client knows about or not?My problem started in 2014 where by these people would take R99 but now they up to R299 but FNB is telling me that they can't block them coz they keep on changing reference s.How do I solve this if my bank can not assist?What surprises me is when a debit is legit I get an SMS to confirm if I am aware of it but an unauthorised one no SMS.How do you explain that?To me it like an inside job because who else would know when I have money in my account?The other thing I have to call using my airtime to reverse a debit that is more then R200 and charged R18.50 to stop where's these schemers will come again month end and pay again and if their debit bounce back get charged R8.50.I am really tired of this problem.