Hi @Anonymous User
Are you based in the UK or Republic of Ireland which makes a difference?
If you are a UK customer then you won't be able to buy a BT Sports pass directly through NowTV.
You can buy a monthly non contract BT Sports pass through BT themselves.
Have a read of this link on cost and how to watch on different devices.
Should you be a ROI customer then go to the NowTV ie Republic of Ireland website for current deals.