N Power had an almighty hen* up with their billing some years ago, essentially they had no idea about how much power many of their customers were using and failed to issue us with a bill in any shape or form for over a year. Our then direct debit didn't change. Eventually they sent readers out to try and sort the issue. They missed us two or three times, leaving a card to return with our reading, which we did, and eventually they sent an abrupt letter telling us they would be at our home at 9.30am on such and such a day and we had better be home! As Lady Byegad was at work, and I had a doctor's appointment at that time, we weren't in. The next abrupt letter threatened legal action if we weren't in between 9.00h and 17.00h on Saturday. We duly waited and they didn't turn up.
I rang them and tore the poor representative a new one, he countered by demanding a time and date for them to read the meter. I chose a Sunday after 18.00h and before 22.00h! The guy arrived at 22.30h, we were in bed and looking out of the bedroom window I waved, pointed at an imaginary watch and refused him entry.
Much threatening correspondence flowed to and fro before they eventually agreed to come on another Sunday evening, this time between 17.00 and 19.00h. The reader arrived, on time, read and left. Two weeks later a cheque for the several hundred pounds I'd overpaid arrived. They had made a smallish mistake, in my favour, but by then I had decided to move to another supplier and kept it.
* Hen, because the male chicken so self-identifies, and the anti-swearing editor change stinks!