Unauthorized debit order!

<p>My cheque account was debited R117.50 without my autorisation. When i called FNB they told me it's from a number ********** . When i called that particular number they in tunr said they got an instruction from ********** . This number just rings. HOW DOES THE BANK ALLOW MY ACCOUNT TO BE DEBITED WITHOUT AUTHORISATION FROM ME? I DO NOT KNOW THESE PEOPLE. On my bank statement it shows Ref: Revolvrew Revo 116872. What is this for?? I am also starting to see a trend with all other people reporting this under FNB. What is the bank doing about this?</p>