*****ulent activities on my card

My card was ****** and the morning after I blocked the card on my app. I then ordered a new card on the app. A week later I saw multiple transactions on the card being used at Toll gates. I went to FNB branch closer to me, contacted ***** and had the card cancelled. Yesterday the very same card that was blocked and cancelled was used again, now I’m being told my account is overdrawn. I’m wondering why is a cancelled card still able to make purchases??