Worst case scenario of my money going missing

Please tell how can money be transferred from a investment account??? So yesterday I transferred R200 from one of investment acc to savings acc so I can pour petrol and withdrawed it by the garage, fine drove home and all... Later I'm checking my truecall messages there I see a transfer made from that investment acc to a RTC reference which I know nothing about and that transaction was done through internet banking and checking the time it was between me driving from the garage to the house. Fast forward to the following day went to the bank queried abt it but I was told that transaction was made by me chance are I know abt transaction so they can't reverse it bluh bluh, and them came thru to complain about it because it happened with a space of 30 minutes after i was using my app. This is the worst experience ever top it off to be told I might have done the transaction, I want nothing to do with capitec like ever!!