If not otherwise suppressed, after the Receipt Email is sent to the customer for the auto order transaction, a second email is sent to the customer which provides them a cancellation link that would prevent any future orders from occurring.
Installment auto order items would want to do this to prevent the customer from cancelling an installment purchase prior to completing the installment payments.
If you suppress the Easy Cancel notification, or in addition to having that go out to the customer, you can provide a cancellation form from your website using the following URL:
Auto Order Cancel form URL:
https://secure.ultracart.com/cgi-bin/UCAutoOrderCancelQuery?merchantId=DEMO
NOTE: You must change the merchantID parameter DEMO to your own UltraCart MerchantID.