I had a similar double billing problem that I posted here about back in August - it's been impossible to get an explanation for why from E.ON Next customer services although one of the community managers here (E.ON Next staff who check in from time to time and step in if they can help) has been more responsive.
The problem appears to have been that the estimated distribution of my energy usage over the winter and summer months was wrong even though my overall usage for the year remained essentially the same. Because prices went up in April 2022, the net effect of that was to reduce my overall charges a bit.
It sounds like the situation isn't likely to be quite the same for you because you have smart meter readings throughout - but it might be worth checking if the new readings align at every step with the original ones, or if it's just the first and last ones that are the same (indicating that overall usage hasn't been altered). If any are different then that wouldn't affect the cost because you're on a fix, but it might explain the reversals and re-billing (because the recorded pattern of usage over the course of the year would have changed).
Not sure if that makes any kind of sense, hope so! As I say, I've found it hard to get a clear explanation from E.ON Next so it's just a thought based on my own recent experience.
Last edited by Emily; 15-10-22 at 14:35.