[LINK] The displayed telephone number

[David]

There seem to be two types of telephone number: a network subscriber-number and a calling-number which is shown when "calling number display" (CND) is available.  Once upon a time when the earth was green, and the network was managed by a public entity responsible for providing a national service, these were usually the same so we could rely on CND to identify the caller.

But now there seems to be no control over this.

I notice marketers have begun picking random calling-numbers with an exchange prefix the same as the called number, presumably so it looks like a local call which the victim will be more likely to answer.

Should providers of voice services be *required* to ensure the calling-number is either the same as the network-number or "Anonymous?"  Is that even practicable?

DavidL.