You can turn off the spam/security number you've registered according to the version of the WhoWho app, as follows:
[V2.4.1 and later] WhoWho App Launch > 'More' Tab > Spam Management / Security Management
[Less than V2.4.1] WhoWho App Launch > 'More' Tab > Registration Number Management
Tap see more > General Setting > Do not Disturb of Notification
But, if you set 'do not disturb' it can be excepted when we announce of recent updated spam phone numbers, event, latest notification and important news sending in future.