Assupol clearly doesn’t listen to its customers

I arranged with Assupol in November and paid my monthly installment to ensure I won’t have to pay it now. I now wake up and see they didn’t cancel this months debit and now the funds have been taken!!!!! Am I now expected to reverse the funds and my own cost???? What was the point of me making the arrangement and paying ahead???? I’ve never been so irritated. Fix it!!!!