I was with British Gas from 2000 for 18 years on both gas & electric. I bought a second house in 2009 to renovating and switched that to British Gas too. In 2011, huge bills started arriving for both properties. I realised that the second property's bill was just an estimate and once I gave correct meter readings to BG, I was hundreds of pounds in credit. I then asked BG to use this credit to clear the bill on the first house, which they did. A few months later another massive bill arrived for the first house and BG took the money automatically. I then realised this was an estimate too! What followed was a campaign of months to get my money back and it was only because of my tenacious nature that I succeeded. I should have left then, but didn't. I sold the first house and went on monthly direct debits for the second. For the next few years a pattern emerged where I would pay £176 a month for about 9 months, then have a meter reading, be told I was over £1000 in deficit, and the bill would go up to £380 a month. The usage was the same, year in year out, so why can't BG estimate a correct monthly debit? I left BG fifteen months ago and have been paying £150 a month to my new company...its late May and I'm £500 in credit - figure that out.