********** activity on my account by Nedbank

Between August and September, there was a transaction of about R600 or R800 that was debited off my account and I was advised it was a delayed transaction from my previous petrol purchase which at the time indicated had been debited on that day. To my surprise when I looked at my banking app on Monday, there was another charge and I was advised it was from my initial petrol purchase which I had made the precious week. Today the same scenario has occured and I have been advised to take my bank statements to the petrol station so they can call Nedbank to confirm that they have submitted whichever documents to confirm that I did make that purchase the previous week once again. Okay so I'm meant to go directly to the garage and fix an error that has nothing to do with me and I'm meant to trust my banking facility. Once again the bank has taken R400 off my balance only to be advised that it will be looked into. Once again I should trust my bank to do the right thing when they failed to rectify this error the last time. How on earth am I meant to trust Nedbank when your not doing justice with my funds ?