At the moment there is the ability to hide own number to the recipient of the phone call or SMS could not see who he calls or writes. This service is also popular among those people who want to play and make fun of their friends, posing as another person.
If you want to know the hidden number of the person who is calling you constantly, ask for help to the mobile operator, who is obliged to provide you with a printout of all calls for a period of time. Usually, it will help you to find a hidden mobile phone number that you called.
If this doesn't help, ask your mobile operator to put a ban on receiving calls and SMS from any hidden rooms.
Also, if you have a modern mobile phone, configure the option of receiving phone calls only from the contacts list. Do this: go to settings, find the menu "Calls" and select "Receive calls only from contact list". This way you will be able to protect yourself from annoying calls at any time of the day.
Some mobile operators provide the service of "Hide number SMS for a small fee. Unfortunately, many users use it for criminal purposes. To identify these intruders - the task of law enforcement. If you are on the mobile phone fray, the many threats or abuse, immediately contact the police who will do everything possible to stop such actions.
However, law enforcement is not always possible to solve the problem situation. In this case, take a printout of phone calls, punch the address of the attacker, shame him and make him forever forget your phone number and never called.