Mate 20 beeping sound

[Android Central Question]

If my mate20 is not on silent, especially after midnight, my phone keeps keeping non stop as if I'm receiving messages.
I deactivated all notifications and sounds. I checked the alarm clock and the timer... Nothing is on... Its frustrating. I also checked all apps nothing seems to be happening it only vibrates on silent and on mute it stops... Otherwise beeps off the hook! Pls help