Supercreator subscriptions are priced per OnlyFans account. Your free page and paid page count as two separate accounts and are billed separately - even if they're linked or owned by the same person.
Two things that help:
CRM Lite is free for up to 10 accounts, so you can keep a lower-activity page on the free plan at no cost.
You can mix and match plans per account - for example, Super AI on your paid page and CRM Lite on your free page.