A new measure under the Ley de Servicios de Atención a la Clientela requires commercial calls in to use a 400 prefix from 17 October. Operators must block any public marketing calls not using this nine-digit code, which functions unidirectionally.
The law applies to essential sectors including energy, finance, and transport, alongside firms with over 250 staff or 50 million turnover. Small utility providers are exempt based on market share. The prefix prevents recipients from making return calls.
The OCU warns this change does not guarantee call legality or eliminate spam. The consumer group is now calling for a public registry to identify companies behind each 400 number, as the new legislation enters its six-month transposition period today.