Debit order for a cancelled policy

I requested that my policy be cancelled and further explained that I can't take calls during the day as I work in an emergency control room. I don't understand why I keep getting notifications of a debit order from you which in turn deducts money from.my account as there's insufficient funds. I feel it's about time I took this to the ombudsman because I cannot incur costs from a debit order that shouldn't be active anymore. Which also reflects negatively on my credit profile