Report malicious/obscene calls
Making a malicious or obscene call is a criminal offence. These perverts get their kicks if you react, technology has now got them on the back foot, and doing things like withholding numbers, and mobile phones, they don't work, as the pervert featured in this site knows, the technology will find em, and the police will gladly prosecute them, so Don't suffer in silence.
DO NOT take the law into your OWN hands, this will only serve to make a bad situation worse, the police Will act, however, they are impartial, and if you deal with matters yourself, you may find that its you they "LockUp", so report malicious or obscene phone calls to the police.
Various laws can be imposed against people who make malicious calls or send malicious messages. If calls are severe and persistent, then prosecutions can be made under harassment laws. The chances of prosecution and higher penalties increase where offences are made more serious by other factors, such as racism.
In cases where psychological harm to victims has been severe, callers have been charged with causing actual or grievous bodily harm.
Report nuisance calls
Nuisance calls can often be resolved without the police having to get involved.
If the nuisance calls persist and you believe that the calls could be related to other criminal activity, or if they cause the victim particular distress, the police may consider investigating them as potential harassment.
And don't forget the civil courts, when they have been convicted, sue them in county court, even if they don't have much money, very often they will have personal liability cover on their home insurance, that can pay out if you successfully sue.
Use the Law, and turn the table on perverts!