You have to downgrade from AT&T ActiveArmorSM advanced mobile security the same way you signed up for it. For example, if you subscribed from your iPhone®, you’ll have to cancel your subscription in iTunes.
Downgrade in the app
Cancel iOS subscription
 Cancel Android subscription
You’ll still have access to all the free mobile security features to help block spam, protect your device from unauthorized access, and more. This will just remove the ActiveArmor advanced mobile security subscription from your account.
FYI: Once you deactivate the ActiveArmor mobile security service, you won’t be able to manage and control any unwanted calls, including blocking spam and telemarketers. The AT&T wireless network will continue to protect you from the default fraud prevention built into our network.
You must complete all steps to deactivate and remove AT&T ActiveArmor mobile security to stop billing. Just uninstalling the app doesn’t remove the service from your account.
If you’ve completed the steps to deactivate the service, you can remove or disable the app on your device.