@Anonymous User
Look for the sort of router facilities described in this article:-
https://uk.pcmag.com/networking/136288/how-to-kick-your-kids-off-the-wi-fi
The Now Help is quite a fruitful source of information, so I hope you have used, or will use, this in your quest,
The Now router is pretty limited for these things, and Now don’t make it easy to replace it with a more capable one, but you could follow the link there for the Circle Home Plus and its competitors.
If you shan’t want to use the internet yourself between those hours, consider a timer switch to power down the router.
If all else fails, other broadband providers supply, or at least let you use, more capable routers,
Set a Payment PIN on your account so that no-one but you can buy memberships on it.
Check your bank accounts monthly for any other unexpected payments to Now.
That way you can at least nip them in the bud, while you and Now figure out whose fault they are.
