I have been with E.ON for many years. I have tried researching alternative energy suppliers, but as I pay at the Post Office and changing suppliers seems so complicated; I've stuck with E.ON. Plus I don't pay for anything online, and of what I understand a lot of energy suppliers only operate that way.
My bills have been getting higher and higher, where I have now written to E.ON asking them to investigate how they have charged me; it's incredulous that on my bill it actually states that I am on the lowest tariff - last bill £444.44 doesn't say so. They have stopped sending someone round to read my meter for quite some time now, even before Lockdown - but they still send someone round to my Mum's house to read her meter. Plus I filled in a Warmfront form a long time ago for supposedly cheaper bills, as I am on ESA benefits for being on long-term sickness; hasn't made any difference.