FNB PLEASE STOP TAKING MY LITTLE MONEY AWAY FROM ME

I had a 1 yr contract that has expired with Virgin Active and after 14 month FNB continues debiting me either intentionally or erroneously. I was debited on the 1st of Sept and I chatted to a banker about this and it was rectified. I woke up today again to another debit order that went off on my account even when i didnt have any money in my account, This is pure ***** knowing that i intentionally stopped keeping money in my FNB account just to avoid this situation and FNB would go ahead with an unauthorized debit order on peoples account without prior notice and the account owners approval, FNB, kindly stop this act and reverse whatever amount you have charge on my account back. i do not owe Virgin Active and I no longer have a contract with Virgin Active. Kindly stop this frustration.