How to Prevent CM13 Calling by Itself? I noticed today that my Samsung Galaxy S4 with CM13 (unofficial Kyasu's ROM) called two my contacts itself; those contacts were those which I keep in my blacklist; which was also why I had react to the incident. 
I have a passlock in my phone so calling itself is not possible without a break into my system. 
This implies me that my ROM was cracked, and used for own targets. 
This is the second time, I notice that my phone calls itself; first time, it called my favorite contact one week ago; in the other end, my friend heard only machine/random noise. 
Therefore, I would like to add additional measures to control the security/privacy of my phone. 



How can you prevent your phone calling itself?
I found out more stable ROM. It was not the official one which has noise artifacts, for instance. 
I found some patches made by Temasek/arter97 here at points (8) and (9). Using them solves the artifact noise problem, which occurs in the official CM13 and kyasu's ROM. I also switched to Temasek ROM which seems to be one of the most used unofficial ROMs. It is the most stable ROM that I have found for the device. It also supports updates directly in the software.