For one student
From the Admin Dashboard, navigate to the Billing tab and then the Statements tab. Find the student for whom you'd like to disable autopay. Click the three dots to the right of their name and then click "Disable autopay".
In bulk
From the Admin Dashboard, navigate to the Billing tab and then the Statements tab. Select the checkbox to the left of any student's name that you'd like to disable autopay for. Click the red "Disable autopay" button in the top gray header row.