Aug 2017:After 6 months of argument with FU refusing our meter reading and making us pay estimated bill I managed to bring the account to resolution, close the acct, get a refund from them, move to different supplier. Dec 2018: I receive a debt collection letter for over £6500???? I am not a customer of them anymore for over a year... They decided to 'review' the account 1 year after I left. Never sent a bill. They are refusing to even apply the OFGEM BACK BILLING PRINCIPLE and are insisting that 2015 is within 12 months of 2018.... hitting my head against a brick wall, Which! Legal team on the case, ombudsman on the case, solicitor on the case and they are still refusing to keep account closed as it was in 2017.... WHAT CAN ONE DO AGAINST THIS?????