...easycinema.com helps you to keep track of what you've got 'out' and what's been received back.
Annoyingly, this latter list isn't so much a thank you for returning them, but more a nag that you haven't written reviews of any of these movies. "Stelio, you 'avin' a laugh, ειναι?' ... Read review
Direct Debits can usually be cancelled through your bank, by visiting the branch, phoning them or, if you bank online, there should be a section on your regular debits which can be reviewed and/or cancelled. Give your bank a call if you need more help, they'll know what to do. Hope that helps!