Telephone numbers displayed to people receiving calls must be valid, dialable and uniquely identify the caller.
About time! Most of the random time-wasting calls that we receive have a spurious number presented which is always one digit short of what a number might typically contain - something of the format 01234 82271.
Doesn't stop them being a pain in the neck - but it means there's nothing meaningful to report.
Banning this will be a first step in the right direction.