Reversal of trasactions

Hello Peter, I mistakenly made a payment to the wrong beneficiary on the 15th of May 2018, I immediately noticed 5 minutes after the transaction and I called standard Bank immediately . I was informed they couldn't reverse the transaction instead they would do trace and recall and its not a guarantee I will get my money. what I failed to understand is even tho I took action the minute I noticed, my bank could not stop the transaction, they cant tell me that the money was already reflecting on the nedbank's account already. now I don't know what to do anymore, where to go to get my refund, please help. its an amount of R2835, that I was to pay for my child's school fees.