Why were the bills so high? Were the bills estimated and did you fail to supply an up-to-date reading? I have no idea what your contract says about payment, but in those circumstances, I'd cancel the direct debit (tell them first in writing) and state that you'll reinstate the DD when all your credit is used up. Keep supplying them with accurate readings in the interim. It's not your job to enhance their cash-flow with your money, just to pay what you owe on time,