*****ing from my account

I got a policy with these people in October 2011 and I set up a debit order with them. After 9 months of paying and no policy documents I cancelled the policy with them. Now almost every few months they reappear and debit my account. I have stopped the debit order several times but they just change the ref number and debit me again. These guys are ******* dont believe a word they say!!