Refuse to cancel my insurance

On 6 June 2017 I wrote a review because I was unable to reach C Sure to adjust my policy after I got an upgrade. Because it is impossible to reach C Sure I decided to cancel my policy at the risk that I might have to claim one day from someone that doesn't seem to exist. They took a week to get back to me but finally assured me that my policy was cancelled and I made sure that they confirmed that no further debit orders will be taken from my account. Needless to say that did not happen and they still have been deducting payments since then. Is there someone that can sort this out for me and get me a refund on the past 3 month's deductions?