We joined BG in May ‘19 and the first seven months seemed fine. Around Xmas they began doubling the monthly DD without writing, or writing and confirming a lower amount. I reclaimed and paid manually to protect my mortgage payments. Battled on to correct estimated start readings. Maintained original payment schedule and initiated leaving early June with a modest credit on the accounts. Received three bills in mid July (after account closure) claiming I owed £154, then £194, then £249. On receipt of first bill, asked BG to prove the debt. Despite regular contact and repeated requests, it failed to do so. In Sept, BG placed 3 late markers on my credit file for the disputed debts (2 gas and 1 electricity), which has derailed an ongoing mortgage application. Raised a claim with ombudsman and discovered that BG had placed us on the standard (most expensive) tariff and backdated this to January, that BG had also increased the debt to £336 added an additional £28 ‘debt recovery fee’ and forwarded to a debt collection agency during investigation by the ombudsman. This is contrary to FCA sourcebook guidance. I have received no justification for the increases after account closure. The markers have reduced my mortgage offer by £80k-£100k and forced us to radically downscale our aspirations. Instead of looking forward to buying our dream home with our two small children we’re are struggling to raise enough to even remortgage our current home! Even after being forced to pay hundreds of pounds in disputed debt in full (on a without-prejudice basis) to its debt collection agency, British Gas refuses to remove the late markers. After following BGs advice to escalate to the ombudsman, BG refuses to speak to/correspond with me on the matter. I am left hundreds of pound out of pocket and essentially unmortgagable! Taking out a British Gas contract ranks amongst the worst decisions I’ve ever made. It’s no exaggeration to state that British Gas have ruined my family's dreams! COME ON, British Gas, do the right thing and remove the late markers. Don't punish my children for the dispute you have with me!