You can cancel your subscription at any time within the year while your subscription is valid. If you request the cancelation of the subscription within that period, you will not be charged for the renewal once your subscription has ended, however, you will not be refunded for the already purchased subscription.
If you have signed up for the Bellabeat+ Free Leaf subscription model, if you cancel your subscription within the 7-day trial period, you will not be charged the yearly subscription fee and you will not receive the option to claim the Leaf, however, this can be done up to 24 hours before the free trial ends.
For more information on canceling the Subscription, please refer to this article - How can I cancel my Subscription.