I have checked with my service provider, it would appear that they are not able to block withheld numbers. My problem is simple, to take calls when I am abroad are expensive. With my iPhone 5s I can clock known numbers.
My good doctor withholds his number so I would like block withheld numbers some times.
Regards,
Steve
Is this perhaps a government issue?
MacBook, Mac OS X (10.7), Computer start up and performance