When BTL changed the billing system a few months ago, the payment desk was telling everyone that payment was now due on the 15th of each month. That apparently was only for that month but plenty of people are under the impression that it was permanent. I had mine cut off last night and when I went in to check up and pay this morning 2 other people came in with the same story. If you pay by today there is no disconnect fee, if you wait until Monday there is a disconnect fee.
There are those who will say, don't you check your due date on your bill. In my case I pick up at the office so I don't bother to check it as I come in on the same day each month.