Visa DMS Link

I have an unathorised transaction on my account "Visa DMS Link" for R38 and I would assume this will not be the last... Please investigate as I am not going to phone FNB directly just to be transfered from pillar to post! How secure is FNB? Whenever I transact on the FNB app or online, I am required to authorise via my phone, why was a transaction automatically processed without my knowledge???? - 'Visa DMS Link'