The monitoring program of the Nine Gods System monitored citizens' communication records, text messages, phone calls, and emails, scans them regularly, and conducts logical reasoning on the data.
The IDs in question will be listed in the "red" List", the city guards will file, and these IDs will be subject to varying degrees of investigation depending on the severity. Although it will not happen all at once, it is always a hassle to be targeted by the city guards.
Therefore, the mobile phone has become an indispensable communication tool in the underground world, and it has also become a prohibited item of the Federation. Federal citizens are prohibited from buying and using cellphones, just like guns and drugs.
In this way, it is also illegal to set up a communication network for mobile phones, but this has been banned repeatedly. Especially in some special areas, such as the border area, and the city of adventurers that has always advocated freedom.