I’ve just tested this on my iPad, and it plays fine here. So there’s no generic issue.
Additionally to @gavs82008 asking what device you are using, what, precisely, happens when you try to play it?
And who is your ISP?
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.