Spain has switched on a dedicated dialling range for telemarketing. From 17 October, companies covered by the country’s customer service legislation may only place commercial calls from nine-digit numbers beginning with 400 — a change that gives consumers a recognisable signal and, in theory, a single switch to silence it. The range derives from a resolution signed by secretary of state for telecommunications Antonio Hernando and published in the official state gazette on 16 April, which gave the industry six months to make it operational.
- A one-way range: 400 numbers are outbound only, so recipients cannot call back or dial them for any purpose.
- A legal firewall: the prefix cannot be reused for customer service lines, which must stay on 800, 900, landline or short numbers.
- A kill switch: operators must offer customers, on request, full disconnection from the 400 range — blocking every commercial call that arrives from it.
- Limited coverage: SMEs, small energy and telecom suppliers, and call centres based abroad remain outside the scheme.
What the 400 range changes in practice
The measure rests on the customer service law passed last year and in force since 28 December, which obliges companies to separate their sales numbers from their support numbers. Telephone assistance may continue to run on 800, 900, geographic or short codes, but mobile numbers are no longer permitted for that purpose. The CNMC, Spain’s competition and telecom regulator, is the body tasked with policing compliance.
Major carriers have already published their assigned lines. Movistar will dial out from 400 00 1004 while keeping 1004 for customer service; Digi will use several numbers in the 400 120 block and display a “commercial call” label on screen; Avatel will appear as 400 887 887.
Who is bound — and who slipped through the net
The obligation is not universal. It applies to providers of basic services of general interest: water, gas, electricity, passenger transport, postal services, telecommunications and financial services. Any other company is captured only if it qualifies as large, meaning at least 250 employees, more than €50 million in turnover or more than €43 million on its balance sheet.
A transitional clause creates a notable gap. Energy, gas and telecom marketers holding less than 5% of their market that also fail the size thresholds are exempt for the time being — precisely the segment most associated with persistent cold-calling.
Blocking, complaints and the limits of the prefix
Cutting off the range is done through the carrier; no source describes a native Android or iOS setting for blocking an entire prefix, although individual numbers can be blocked and third-party filters such as Truecaller, including its guardian mode for families, add another layer. The free Lista Robinson registry, run by the Spanish digital economy association, removes consumers from telephone, postal, email and SMS advertising.
Two further consumer protections come with the law: marketing consents expire after two years, and contracts signed during calls that were never authorised are void. Breaches can be reported to the telecom user service office or filed with the CNMC.
The structural weaknesses are harder to fix. The 400 mandate governs Spanish numbering only, so a firm that relocates its call centre abroad can keep dialling exactly as before. Origin spoofing remains feasible until end-to-end authentication is deployed, and pattern-based blocking will always trail the spammers. Regulators have moved on adjacent fronts: since June 2025 carriers block international calls and texts that fake a Spanish origin, and from 15 September 2026 they will filter SMS sent under a sender name not registered with the CNMC. Operators are also required to block calls that show signs of being commercial without the correct code, though that detection only triggers after an emitter has already made many calls.
There is a newer risk, too: overconfidence. A 400 prefix does not prove a call is genuine, so anyone claiming to be your bank or your carrier should be hung up on and reached through an official number instead.
The 400 range is a genuine improvement in transparency, and it hands households a blunt but effective mute button. What it does not do is touch the industrial-grade spam that originates outside Spain, nor the small utilities and phone resellers that have made unsolicited calls a business model. Its success will depend less on the numbering plan than on how aggressively carriers filter traffic that ignores it and how readily the CNMC issues penalties. Until both happen, disconnecting the 400 range is a useful filter — not a shield.