Once your account has been upgraded to paid membership, a subscription is required to continue playing. It can not be reverted to free access to the game. The same is true for legacy Shadowlands subscriptions which have upgraded to full paid subscriptions.
For more information regarding premium membership and the benefits you receive, please refer to the following page on our website: https://www.anarchy-online.com/membership-rewards/
If you prefer to play for free, please keep in mind that you can register a new free account at any time through your account management page at https://register.funcom.com/