We understood our bill was based on the new smart meter readings but after a few months realised that we were being charged a lot more than the monthly figure on the meter. In addition our monthly payment on the budget plan was far more than we were using or would use in winter and in 3 months we had built up a credit of £475. It took me over an hour on hold to get through to customer services. To be fair the person I spoke to was competent and helpful and it turned out that the connection between our smart meter and UW had failed and my bills were based on estimates well over what we were using. However only the most recent bill stated the reading was estimate based. The earlier ones said incorrectly that they were meter readings I also cancelled the budget plan and it was agreed that a technician would be sent out to look at the meter. They told me I was due a refund of £845 and it would be paid in 7 days. Watch this space!! It concerns me that people who are busy/technophobic/ visually impaired etc might not notice what was going on and think it was all due to the high energy prices and not notice they were being seriously overcharged in the event of smart meter failure.