Raise an official complaint to the company - and put in bold at the top of the letter to emphasis this point. include as much info/evidence as possible, then tell them they have xx amount of days to respond/resolve as per their complaints procedure and if you don't have a response that you will go the ombudsman.
http://www.ombudsman-services.org/energy.html
this... seriously - if you're getting messed around by call centre monkeys and have explained the situation via phone calls/e-mails to the utility company but are getting no joy... just go the the ombudsman - it will get their attention... ditto to most industries with an ombudsman service - management will have to get involved, they'll have to waste time dealing with the complaint etc..etc.. you'll get someone with a few braincells to at least look at the case and you might well find that they'll realise they've screwed up pretty quickly