Unauthorized debit

I called onecard in May to cancel my insurance with them , they refused to do so . I then went to my bank to stop the debits from them 3 times and they still manage to debit my account to a point that my important debits bounce . I am very disgusted and angry at this poor business practice because as a consumer if you do not want services from a provider it is my legal right to cancel. I want onecall to cancell there insurance as i have no need for it no more and also to pay back all the bank charges i sustained as a result of there poor business practice . I will also take this up with the relevant authorities to insure this never happens again .