Go to the Sophos Mobile Control Self-Service Portal and log in with your Active Directory credentials.
Click on the device you want to uninstall Sophos Mobile Control from. Click Select an action, then click Decommission.
After decommissioning the device, click Select an action again, then click Delete.
On the device you just deleted, uninstall the Sophos Mobile Control app. Go to Apps, then swipe to the page with the Sophos Mobile Control app.
Hold your finger down on the app until a menu appears at the top of your screen. Drag the app to the uninstall or remove icon in this menu. (This may vary depending on the manufacturer of your device or the flavor of Android.)