inconsistency debiting

My name is Jacqueline Maluleke, i have a policy with which i arranged a debit order with them. They keep debitting inconsistence premium amount. i questioned them, trying to fix it and they were rude and said they don't know why. Last month, my dad passed away. I claimed they wanted me to pay for the shortfall when I claimed. I've paid it, but this month they continue debiting the wrong premium amount. Could they be a ****?