Now supply the same router, no matter which of their broadband services you use.
So if you upgrade from one of them to a higher one, you won’t get, or need, a new router for that reason.
You might want to ask Now why your broadband isn’t any faster on the upgraded package, though.
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.