Mark has brought this to us :
I've decided to implement a very agressive call-blocker which blocks
almost all unknown callers (i.e witheld, faked numbers etc). This has
taken a long time for me to decide, but I think the risk of missing
the odd legit call is worth it.



That is what I do, only the known to the phones numbers get straight
through, the rest can deal with the blocker. Any valid organisation
will follow the procedure and get through the blocker, they are used to
them.