On your Mac or PC:
Log in to your RetroCrush account. In the upper right-hand corner, hover over your Account Name. You will see the drop-down appear. Click "Account," and on the page that appears, click the subscriptions tab. You will see the following text and prompt below. Click "Cancel Subscription"
You will then be directed to the following page to select a reason for cancellation and confirm your cancellation.
Click "Confirm," and you're all set.