AT&T has released a new software update G890AUCU6DQE1 for Galaxy S6 Active. The update includes a fix for intermittent call failure issue as well as Android May security patch to the device.
The new Android May security patch brings fixes for vulnerabilities and exposures in the Android OS. Also, the firmware update includes device stability improvements, bug fixes and further improvements for performance.
Software Update G890AUCU6DQE1 for Galaxy S6 Active is rolling out as OTA update with download size around 209MB. The updates will gradually release to everyone. However, you can also check manually for updates, Go to Settings > About device > System update.