reversal for unapproved online transaction

I am utterly concerned with the security of online banking regarding FNB. During the late hours of the night , i received a notification of an online transaction done with a US merchant titled “Kindle svcs”. This online transaction went off WITHOUT MY PERMISSION. I WAS NOT SENT AN OTP PIN TO APPROVE THIS TRANSACTION. I was completely shocked at the sight of this notification as i have no relation to this merchant nor its services. After contacting FNB to reverse this transaction, i had no help or immediate assistance. I was told to contact ***** Department on their cellular line and that was it. Their line never works and i am extremely frustrated with FNBs poor service. Moreso appalled by the lack of security regarding these online transactions…how can they go off when i have never approved it . Highly highly disappointed with FNB.TO DATE THIS TRANSACTION HAS NOT BEEN REVERSED