DEBIT ORDER TAKEN AFTER CANCELLATION

I HAVE BEEN TRYING TO CANCEL FOR OVER A MONTH AND EVENTUALLY SOMEONE PHONED ME AFTER MY SECOND HELLOPETER COMPLAINT YESTERDAY, I WAS IN A MEETING SO ASKED THEM TO CALL BACK, THEN I PHONED BACK AND LEFT ANOTHER MESSAGE BUT NO ONE BOTHERED TO PHONE ME BACK. SO AFTER THEY WERE AWARE THAT I WANTED TO CANCEL, THEY STILL DEBITED MY ACCOUNT???