When someone withholds their number, instead of just putting the call through with total anonymity,
why not send us a specific withheld number code which means absolutely nothing to us and still shows as a withheld number thus maintaining the callers right of anonymity whilst also maintaining OUR right to block that particular withheld number code (WNCer) from calling us again?
The only people that wouldn't be happy with such a simple fix are the WNCers we need to block.
Simples!