To cancel, click your name at the top right of the dashboard and open Account Settings. Click Manage Billing and cancel there.
When you cancel, you retain Pro access through the conclusion of your current billing cycle, after which your account reverts to the Free tier. Any credits purchased remain permanently on your account and do not expire. Your profile, subscriber list, and content are preserved and not removed.
On Free, you can't send email to your fans, the 50 monthly email credits stop, and paid content no longer shows on your page. If you bought a domain through BCKSTG, it keeps renewing every year. Turn off auto-renew in Domain before you cancel, or email support@bckstg.co and we'll do it.