If you are using Shift4Shop's Recurring Orders add-on (a.k.a. Autoship), your users with recurring orders may cancel the orders themselves by using the following steps:
Log into their customer profile on your store by using the My Account link.
Once there, look for the "Recurring Orders" section, which will list their recurring orders.
Click on View Details of the order they'd like to cancel.
At the top of the order, they'll see functions available to change the frequency, date and payment method used on the order.
To cancel the order, the user will simply click on the Cancel This Order button and be on their way.