Unfair debits

I took a policy with FNB last year in october however and cancelled the policy in January and they also confirmed but they are still debiting my account till now and when I call them to find out what is going on they responds is they dont know cause on their system it is showing that the policy was cancelled and they are unable to reverse all that money that has been taken so it means i am busy donating money to fnb for their financial gain.