This article describes how you can interact with Square subscriptions that you have already created with the official Gravity Forms Square Add-On.
For information on creating a feed that will turn your form entries into subscriptions, refer to following reference guides:
If an entry has triggered a Square subscription feed, its entry detail screen will show a Subscription Details box including status, start date, subscription ID, and recurring amount. If the subscription is active, a button that will allow you to Cancel Subscription will also be available.
Canceling a subscription can only be done from the Gravity Forms entry record. Square does not currently provide an interface for canceling subscriptions. Thus if an entry is permanently deleted, there will be no way to cancel the associated subscription.
Entries that have a subscription status of Active will display a Cancel Subscription option in the Subscription Details section of the entry detail. Clicking the button will cancel the associated subscription.