FNB allows debit order to go through after stopped!!!

I have cancelled my Gym Membership with Planet Fitness. And then cancelled my debit order at the bank. (22 Aug) FNB So for one month, my debit order didn't go through, and the 'stopped' debit order worked well.

Then on 26 Sept, FNB allowed the debit order to deduct again, and also the arrears month that did not collect... How can this be allowed. I was transferred about 7 times when trying to get this resolved, all to end with a consultant telling me that If I stopped my debit order, I must remove my details (not sure from where) to ensure it doesn't deduct again. WHAT??

So for one month it was stopped, and then deducts again, and now I suffer the loss? This is theft.