I recently had a problem with a very large water bill. I read everything on your site and stayed calm
Contacted Customer Services and got zilch
Rang them up again and asked them to speak to a Manager....didnt expect it to happen....but a manager phoned me an hour later and said he would look into my problem

Result

an hour later he phoned me back and said it was a computer error.
The following day I received a revised bill and a couple of days later a letter telling me I would get £30 credit off my next bill.

I was well pleased as I hadnt asked for any compensation...just wanted the problem solved.

Thanks for the help it was very useful

Cheers