Billing error and now suddenly I owe Octopus £800

masonic

This is a well known issue that has tended to be associated with Bulb (but to be fair there have been reports with several other now defunct suppliers too). See, for example: https://forums.moneysavingexpert.com/discussion/6434412/bulb-economy-7-transposed-readings

This does raise another question around your usage and E7. If this corrected usage now results in such a substantially higher bill, it suggests most of your usage is in the day at peak rates, and only a small amount is used off peak. If that's the case, you'd probably be better off on a non-E7 tariff (in which case you may have success asking them to bill you on single rate for the whole period rather than writing more off). If you know the bulk of your usage is at night, it could be that your original billing was correct and the recalculated bill is wrong. As per thread linked above, check on your meter which register is active during the day and make sure that's the one that's being billed as day usage.

mathilde

For anyone interested, I went back and forth with Octopus a bit and they took off £100 so now the debt is £700. They offered a payment plan but I'd rather pay it off ASAP.  I hate carrying debts. I'll get it paid off by the end of December. 

I think the moral of the story is ask for detailed statements and check them. When I got my credit refunds earlier this year, they said, "Sure, we'll just check the account" and then they sent me the refunds. I was toodling along assuming I'd get an end-of-year statement. Don't toodle.