How can you see who is calling you with hidden number in Greece

Many Filipino in Greece have had the misfortune to accept calls in hide which is very annoying and often have the form of a "prank". In some cases the calls are confidential number, slanderous or even threatening. All you can think of anyone who receives such a call is how you can stop the person who calls. 
And yet there is a solution and if you do not know the details of the person who is calling you, you can find out the number of him by using the ways bellow.
Contact your service provider communication use and ask not to receive calls from hidden numbers in Greece  . If you do this, when someone calling you with hidden number shows that you talk(buzy number). You can also request the provider to remove the hide caller id for a limited period, to identify nuisance or malicious calls (Law in public 1853 - 21.12.2006). In the latter case anyone calls you with  hidden number will hear a recorded message (even before you answer your phone) that the concealment has been neutralized. 
Once you know the number that is calling with hidden number you could ask for the identification of the person who is bothering you. Prosecutors, and preliminary and investigative authorities, let alone the Judicial Council and the courts are entitled to require a provider of communications services over the internet electronic traces of a criminal act, the i-records (call number, caller - called, call time, etc.) and identifying the person in the corresponding electronic trace  and the provider shall be handled without the need for prior authorization and an authority especially Authority Privacy of Communications (ADAE).