********** online purchase

Today the 6 November 2018 at 10:09am I received an email notification that I made a purchase and I immediately called FNB telling them about the email and confirming that it wasn't me. First consultant hang up on me, second consultant told me she can't help if I don't have my card with and third consultant said she can only open a ***** case.

Firstly I didn't have enough funds for the purchase to go through but to my surprise I was told by FNB that they allowed my account to go negative when I had never ask for such a facility and this purchase would have declined if this was not the case.

Usually FNB will send a notification so to authorize the transaction but this time that did not happen. I know I was told there will be investigations but who must take responsibility for this because I want my funds that were there before this ********** transaction took place?