How to deal with telephone nuisance calls

One reader suggests speaking in Welsh and asking the caller to speak in Welsh.  There is an English - Welsh translator available on line to help you say the appropriate words:

http://www.etranslator.ro/translate-english-to-welsh.php

Also, on YOUTUBE, there is a selection of videos on the subject, here's one for you to look at:

At the end other similar videos can be selected.