I remain undecided as to the origin of these calls, i.e. random or attributable to leaked data.
Many of the calls we receive will address us by the subscriber name (which is not me), and they know our street address, so they could either be random from the phone directory, or leaked data.
Others will address me as 'Mr Muddle', which appears in no directories and so are clearly attributable to data leakage. On one occasion many years ago, I pinned a marketing call (from one of the energy providers) to a certain National hotel chain, where I had checked in with a slightly different name, and the caller addressed me by that name. The reason I did that is a long story, but I promise nothing embarrassing or sinister.
But with PPI calls and the likes, it is just a recorded message, '
You are entitled to compensation, press 5 to talk to an advisor'. When I press 5, the advisor has not the slightest idea to whom or to what number he has been connected, and so I suspect they are just calling semi-random numbers. Not totally random obviously, they'd restrict themselves to valid UK dialling codes and the 'random' numbers would be valid formats, but nothing more than that.