The article actually mentions the TPS in the case study: "But it was after he [Martin Shelley] registered with the Telephone Preference Service (TPS) – a list

The article actually mentions the TPS in the case study: "But it was after he [Martin Shelley] registered with the Telephone Preference Service (TPS) – a list of people who have indicated they do not wish to receive sales and marketing calls – that the number of unwanted calls increased." Apparently it's not working as expected ...