Due to some bad apples who created spam campaigns on the free plan, we can no longer offer that plan. It's quite unfortunate as a few bad apples have essentially prevented us from offering this plan.
The pro plan was discontinued as well because Facebook decided that due to these bad apples, they had to ban our domain.
Due to this, we're creating a new plan in the future that will allow subdomains, but have lower limits than the enterprise plan. Stay tuned for this announcement.