To cancel an active plug-in subscription first sign in to The Collective website and go to your account page: https://collective.focusrite.com/my-account/
You can see which plug in you are actively subscribed to, to cancel the subscription for any single plug-in click "Cancel Subscription" and then "Yes, Cancel my subscription."
You'll be asked to provide some feedback and then be unsubscribed from your subscription and receive an email confirmation.
In your account, you'll be able to see the new subscription status
Your plug-in will still work in your DAW until the term ends, at which point you'll only able to use it in Demo mode. When you resume the subscription you'll continue contributing to the total purchase price.