Thanks for all the anaswers Ben, Gavnad, Hell's child and SirSimon
I rang NTL. I asked them if I could change my billing period back to what it was over Christmas. THey said it wasn't changed. I asked them to pull the old bill up. They did, eventually and said we can't understand this it must be a glitch!! Anyway they say they can not change the billing period without asking central accounts (Who ever they are cos I never heard of 'em) first.
So I am phoning nearly daily in an effort to get them to change it !
Seti^