OppoK9X mobile phone notification sends text messages loudly.

1, Settings-Sound and vibration-Mute mode-Turn on full mute function.

2. Check whether the phone is turned on in Do Not Disturb mode: Set-Do Not Disturb mode.

3. Whether the mobile phone turns off the switch of the notification center: Settings-Notification Center-Information-Allow notification, status bar display, and screen lock display (at present, only the ColorOS2. 1 system has this function).