Numbers are not being blocked!
Make sure the app extension is loaded.
Simple Call Blocker works by feeding phone numbers to block to the Phone app via a “Call Directory app extension”. That directory extension must be turned on.
First, check the app’s Status screen to see if the blocker is enabled, and if the blocker is loaded. If the blocker is not enabled, follow the on-screen instructions to enable it via iOS Settings.
Note that iOS does not tell you when numbers are blocked.
Blocked numbers do not make your phone ring and do not show up in your list of missed calls. Blocked callers can still leave you a voicemail; there is nothing that a call-blocking app can do to prevent that.