@Anonymous User
Absent anyone offering you a more focussed fix for this, the unwelcome, but prevalent, Sony advice is that you should Factory Reset the TV.
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.
