We used to get nuisance calls years ago that went on for a few months - had to change no. to get rid of the problem.
Often wondered since if you just left the phone connected to the call indefinitely would it hold up their line and cost them dearly? With mobiles these days as a backup it would not matter so much if the landline is held up by this indefinite call.
If "little chat" is a euphemism for "threatening" him as you mentioned earlier then I, for one, would not recommend this as a suitable way to deal with problems such as this due to the risks involved.
There was no risk involved..He could hardly report us now or anything to the Guards..It was a quick fix to an annoying problem..It would of taken months for the guards to do anything