Once you've logged into Donorbox, click the "Recurring Donations" tab at the top of the page.
You will then be brought to a list of all your recurring donation plans. Find the plan you wish to cancel and click the "Edit" button on the right.
Then, click the red "cancel button.
Canceling PayPal Recurring Donations
Paypal recurring donations are managed on the donor's PayPal account. For the most up-to-date info on how to cancel PayPal donation please go to https://www.paypal.com/us/selfhelp/article/How-do-I-cancel-an-automatic-payment-I-have-with-a-merchant-FAQ2058