arpat123:
You are entitled to be upset about Eon's treatment but hold back on the rant and focus, focus, focus on the consumption and the billing.
First of all, when you passed the final gas reading in July 06 did Eon request a forwarding address and what was your response? Not to request a forwarding address would be a clear breach of the closedown workflow.
Next, there cannot be actionable billing arrears unless there has been atleast one bill unpaid. You need to take steps to obtain copies of all the bills issued. Ask Eon nicely and if they refuse or propose excessive charges make a Subject Access Request requiring the provison af all the information held, including copy bills. This will cost you £10 but is money well spent.
In parallel, consider setting down all your issues as a formal complaint strictly in accordance with the Eon complaints procedure, in writing, by Signed For delivery. This must be responded to in a specified timeframe and if you remain dissatisfied at the expiry of the timeframe your are entitled to invoke the alternative disputes resolution procedure. This costs you nothing but Eon a hefty case fee regardless of the outcome.
If you were asked, but didn't provide a forwarding address, fighting this is slightly harder but if you weren't asked or you were and provided a forwarding address and Eon cannot substantiate that further bills were sent to that address, in my opinion under the 1 year rule there is nothing to pay.
You need to push very hard and see what gives.