Nuisance Telesales Calls (additional)

I had a nuisance telesales call yesterday from a number which was not "withheld" in the formal sense, but simply anonymous, as it originated from overseas. After a quick check with a BT operator it seems that, unfortunately, these anonymous calls from overseas cannot be blocked under the standard BT system.

The rationale for this seems to be that, as it is not a recognised withheld number, but simply a number that is not recognised as having any characteristics at all, BT must allow it access. I can see the case for this. More accurately, I can see why there should not be a case against this.