Where is my money going

I have recently realized that nedbank is double charging me for my petrol swipes and one withdrawal. I went to the Newtown branch to try and understand what has been going on. I was realy surprised to see that the slips that I have for my petrol swipes don't correspond with my bank statements, money goes off as I swipe and when it reflects on my bank statement. When I ask the lady at the branch she tells me that the transactions were not yet authorized that's why this is happening, for the past 3 days I have woken up with money disappearing on my Acc and no one knows where it's going to. Transactions that I have not done are reflecting on my statement. All I want is my money back