Abyssmal service. When tenant left, it was found she had had a prepayment meter installed due to debt. We were unable to get any energy at all without acquiring from Npower a Gas prepayment card, and resetting the Electric key which had been left behind. Paid for every unit of energy used, and left meters in credit, giving meter readings when we took the property back and when it was sold. We are being bombarded with demands for money which we quite clearly do not owe. NPower are stating our account nos which are incorrect, meter readings which are non-existent and not possible, due to meters having been changed to prepay in June 2014. One of their operatives came to check and read meters, by appointment, but still no joy. What can we legally do to get these cowboys off our back? So far off the scale, they would not even get one star.