No, it is not possible to disable the careers page with an active subscription.
If you end your subscription, all of your jobs will be archived, removed from the careers page and job boards, and candidates will no longer be able to apply. The Workable-hosted page will still be accessible, but empty.
To completely remove your careers page you will have to permanently close your account. When an account is closed you will no longer be able to log in and will permanently lose all access to your jobs and candidates. It may not be possible to recover this data once the account is closed.