On the O2 Network in Germany my Cyanogen Phones all receive very annoying Mobile Broadcasts with just a Number in it.

I am guessing these are leftover Messages from Cell Tower switches or the like. They occur most often when travelling or in my home which has very bad reception.

Disabling the regular Mobile Broadcasts (Amber alerts) in Settings did nothing. So I had to figure out how to switch it off.

Open a console and become root(su). Then Look for the right Package in Android

#pm list packages -e | grep 'broadcast'
package:com.android.cellbroadcastreceiver

Disable it

#pm disable com.android.cellbroadcastreceiver
Package com.android.cellbroadcastreceiver new state: disabled