Yes, you can cancel the subscription at any time.
Login to your account, click on your profile and select “Account” from the profile menu.
Go to the “Subscription” tab and click “Cancel Subscription”.
Your subscription will expire after the end of your billing cycle and your plan will be converted into the free plan.
After subscription expiration, you’ll retain access to your delivery tests but you will not be able to do new tests until you buy test credits or re-subscribe. Unused credits left on the balance will expire with the subscription.