In the past I have had arguments with both NPower and BG about DD payments. About 12 years ago was with BG and out of the blue they raised my DD from £60 to over £100 P/M which would have meant a surplus of many 100's of pounds by end of year - I wrote them emails and letters asking them to check and gave them 3 weeks to get back to me otherwise I was leaving, they did not reply and I changed to NPower, a week later a letter arrived from BG saying their accounts dept had made a mistake and did I want to stay with them - (fat chance). NPower did something similar after I had been with them for a few years so I moved to Cooperative energy about 5 years ago - as well as saving about £400 a year their DD was spot on and needed hardly any adjustment for years, they wrote to me recently to apologise for putting my dual fuel DD up by £3 PM, what a difference in attitude to the members of 'big 6 energy supplier mafia cartel'.