Follow the steps below to cancel the sustaining gift cancelled autoresponder.
  1. Select Fundraising > Donation Management
  2. Select the All Donation Forms tab
  3. Find your donation form and click Edit
  4. Skip to step 5. Configure Autoresponders
  5. Click Disable next to "Sustaining Gift Cancelled" 
If you don't see the disable button, then that means it is already disabled.