This notification bell is the only one that shows you that you have unread messages and emails, but it doesn't display a preview of them. In order to see who sent you a message, you must tap on the bell, which, basically, unlocks the phone.
Since the release of the ZTE Axon 7 in the United States, many owners have complained about this issue. Luckily, ZTE has listened to its customers and decided to act. The latest software update pushed to ZTE Axon 7 units makes the notification bell optional, but no one will probably want to use it anymore.
But that's not the only change included in the update. ZTE also confirmed that there's a new application management policy, which should further enhance battery life. Some improvements to the camera have been implemented too, so expect the video camera focus on moving objects to work much smoother.
The Visual Voicemail has been fully optimized for dual-SIM functionality. There are also some bug fixes and other general enhancements that ZTE added in the update. For example, the .FLAC file playback problem has been addressed, along with the Mute Call issue.