Some two years ago I switched gas and electric to NPower from BG.
I cancelled my direct debit so that I could provide a final reading and pay the final bill by cheque. It is my experience that this works best.
I received my final bill but the last credited direct debits were not included. I deducted these amounts from the final bill and paid the balance.
I eventually received some months later 2 bills equal to the amount I had deducted. I phoned - person agreed with me, gave me a number to phone - but help for ages on an expensive line. I wrote instead - no reply. More bills and red bills, I phoned - person again agreed with me - expensive phone call told to write. I wrote no reply. More bills - I wrote to collections dept. no reply. I received a Debt agency letter - I contacted them and explained. They asked for all relevant papers. I sent copies of the letters. They agreed there was no debt and said that they had referred it back to BG.
I received a letter from BG (hoo-b****y-ray). It explained that the full amount of the bill was correct because they PRE-CREDITED their direct debits so although I paid on the 3rd of every month they credited my gas/electric accounts on the 28th of the previous month with the amount that I was about to pay them !!!! (So obvious really I should have realised

). Also they had no record of the final amount I had paid by cheque (although it appeared to be accounted for on my final bill). Could I please send them a copy of the cheque I had already paid together with the £35? outstanding.
I replied in writing stating that I didn't really accept their version of pre-crediting as this sounded highly dodgy. But that I would split the difference with them considering I had now had a lot of harassment and additional expenses in simply getting any kind of feeble explanation from them at all.
I heard nothing for a year - until last week I was refused a credit card - which is unheard of for me - I must have one of the highest credit scores in the country. It's really excellent usually. I obtained a copy of my experian file which shows 2 defaults - each for £35. These amounts are wrong as I think technically on their books I would owe £17 on gas and £18 on electric. On my equifax report there is no elec/gas but there are two enquiries from someone called wescot with reason stated as "debt outstanding".
I don't know where to start - I don't think I can use a CCA as it's a utility account and not a credit agreement. If I write to BG I don't suppose I will get a reply unless I can make it sound 'official'.