Your subscription has been implemented via direct credit card payment with a payment gateway that manages the recurrent payments.
Therefore, if you don't want to use the platform anymore, you need to cancel your subscription to avoid being billed again.
Check how to do it in the step-by-step guide, below:
1) Login in your Mind the Graph account.
2) Access your profile page.
3) In your profile, click "Details" in the upper right corner.
4) You can see your "plan details" and with one click cancel your plan:
5) If it works, you'll be redirected to the confirmation page showing that you canceled the recurring payment.
Upon cancelation, you will still be able to use Mind the Graph until the end of the subscribed period. After that, you will be downgraded to the free account and will lose access to your creations.