That just sounds like a shitty company to be honest - unless the readings are way out of expectations they should never not except them. And if they are way out of line then they should be sending a meter reader around to confirm them, not just ignoring what you give them.
The ONLY reason any energy company should ever bill to average use over time (an esitmated read) is because ones not been provided.
I'm surprised that the comapny let it go as far as getting to Ofgem to be honest, costs them a lot of money when they get involved.
I gave them actual readings on change over, nothing said at all, first month I put actual readings online and it came up as readings too low, following month the same, so queried it, oh and they increased my monthly payment in that time, no joy getting answers from them so contacted the ombudsmen.
Seriously, I just saw as typing another expensive tv ad, that is totally false, I do not think they will be around long, the customer service is disgraceful, trying to ignore that I contacted the ombudsmen was pathetic, they obviously had no idea how it works or thought I did not.
The thing with all this switching, is headaches, the same monthly payments, no matter who you switch to, and no obvious money saved and no price competition that I can see, they are all trying to be the greenest, but that is bollocks, my power comes down the same cable from god knows where, not directly from that company.
Time to pick one and stay there, nothing to be gained by switching except maybe a cup of coffee a month, on paper, it does not seem to translate into cash.