I’m not sure that spying on someone’s mobile phone is decent… However, a few years ago I had a terrible story with my niece. When she was 13, she got into trouble with a group of 16-17 year-old girls. She started dating with a 16 year-old guy and it turned out that one of his former girlfriends felt jealous about it. That girl was blackmailing her for a long time. She grouped with her friends to terrorize my niece. My sister’s daughter was so frightened that she was afraid to share with us… We had to use spy apps in order to control these abusing actions. On this resource:
http://www.phonespyapps.com/spy-apps-reviews/ we found some details on how to block undesired calls. Of course, getting remote access to a phone is impossible, but my sister and I decided to present my niece a new phone. We’ve installed a tracking app beforehand. It helped us to get the phone numbers of those blackmailers and finally get rid of them. But we no longer try to track my niece’s calls or messages, that’s immoral… We protected her once but we aren’t going to get into her personal life any longer…