Bad bad service to reverse unknown debit order

I got a message that 300 has been debited from my account. I don't know the debut order, called fnb using R70 airtime already only to be told I need to call using another phone because the one I am using doesn't support the verification process. What is that? And I am still going to pay for reversing the transaction! I think FNB allows these debit orders because they benfit from them. Disgusted! Please call me, I will not spend more airtime on this otherwise it's time for me to move on.