With NOW being a streaming service they have no obligation to a contract. Unless your billing is through BT, where it will be BT that you deal with.
The link below is a full explanation of the changes that took place and was highlighted in your account about a month in advance.
This is purely a ploy to no doubt enhance the Boost membership. Which a lot of people obviously disagree with the move.
For most if they already had boost for 1080p and 5.1 sound which I had and therefore remain completely unaffected by the move.
FYI that I do not work for NOW, just a NOW customer trying to help