Your subscription has been implemented via a paypal recurrent profile. Therefore, you need to access your paypal account to cancel it.
Check how to do it in the step-by-step guide, below:
1) Login in your Paypal account.
2) Click in the gear symbol upper right corner to access your configurations/profile
3) In your profile, click "Payments" to access your recurring payment profile
4) In payments, you'll see "Automatic Payments" and select "Manage automatic Payments"
5) You'll see all your preapproved payment profiles, with the expiration dates. Click the one you wanna cancel.
6) Click here to see the payment history and/or cancel it.
7) A confirmation pop-up window will appear. Click "Cancel Profile"
8) Confirmation page showing that you canceled the recurring payment.