If it’s a Sony Android TV, you can watch on the native Now app provided there.
if your Humax box is a YouView box, ditto, but you can’t get subtitles, for some unfathomable reason.
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.