How to Prevent CM13 Calling by 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.