@
Vinzc
Firstly I would just carefully go through the bills from the estimates to the latest bill, hopefully now showing corrected meter readings. Do this with the full pdf bills, not the basic 'abbreviated' online ones. Check all readings and breakdowns, energy used etc. and see if any adjustments have been made. Chances are, if you have submitted accurate readings more recently, everything should have come out correct. If not, you will need to highlight any discrepancies, especially over any changes in tariff, and then contact E.On Next to have things corrected if your figures are in dispute.
More than that, the only way round the problem going forward is to really keep on top of sending accurate readings and never letting estimates drift too far away from reality.
In my experience, the online abbreviated bills should only be treated as a heads up. Always open or download the full version to see much more detail.