Debit card *****

I had a transaction *******ly go through on my account which I know nothing about. The transaction went through on 23/12/2019 at Cash Crusaders Umlazi. I moved from Umlazi in August last year. How can I get my money back because the FNB app does not allow me to report the transaction. This is the second time this happened. The first one went through on 02/12/2019 the amount was 799.90 and the second one was for 1400