It said that the CC would not automatically be charged at the end of the trial.
However, there's no way to cancel/close your account before the end of the trial and there's no way to remove billing information either.
I ended up emailing support@ghost.org
The reason I cancelled is because the only theme I found I wanted to use (Doks) was $149 per domain.
I found that I can have Cloudflare Pages auto deploy my private Github repo's markdown and render with Docsify (which doesn't need a build step). I still used a build step to automatically generate _sidebar.md and populate it with links based on tags found in each markdown file.
The way to cancel a trial is to go to the billing area in the product, then click on "Cancel" - red link at the bottom of the page. That instantly cancels the trial and deletes the account.
If you don't cancel manually, and the trial ends, then we still automatically cancel and delete anyway.
Do no use this product. It's bad before even registering.