Not attending to *****ulant activity in my account

I have a saving Aspire Account with FNB since 2021..I have been using my card recently I have a expirienced a lot of unpaid item which charge R135..I have asked for a proper explanation as what could be the cause but with failed,went to the branch who advised make a call but still no explaination..Every transaction I make the next morning I will recieve an unpaid item of R135 which add up to R720 in a space of 2weeks..