i think its your phone policy for app notification.
find like below link, to find OGNotifier
https://www.techrepublic.com/article/how-to-disable-persistent-notifications-in-android-oreo/
please set OGNNotifier Notification with NO SOUND.
find like below link, to find OGNotifier
https://www.techrepublic.com/article/how-to-disable-persistent-notifications-in-android-oreo/
please set OGNNotifier Notification with NO SOUND.