First: good morning, because today is better than yesterday if you’re tired of being bombarded with commercial calls, because today, Saturday, October 17, 2026, the latest measure by the Spanish government’s Ministry of Digital Transformation against spam goes into effect: starting today, companies can only make commercial calls from nine-digit numbers starting with 400. If you know this concept before you pick the phone easily you will pick the phone easily wants to sell you something.
essential. This new measure comes after the BOE released its resolution in April: There is no longer a valid number range for commercial purposes, however attractive they may be. And they are one-way: they only serve to call you, you cannot call them for security reasons: this prevents possible fraud by calling back an unknown number.
Of course, there are nuances: in the middle of a customer service call they can inform you about an offer, but only if it is related to the solution of your question, complaint or incident and they also improve the conditions or the price (as stated in Article 16.2 of Law 10/2025, Law on Customer Service Services).
How can you recognize a commercial call?. What changes for the user is that you will be able to recognize a commercial call just by looking at the phone number and from there you will be able to answer, filter or ignore it. What’s more, we can even ask our operator to directly block all incoming calls with that prefix.
Be careful, having a 400 prefix does not guarantee that the call is legitimate, but it is a signal that the customer service of your bank, energy company or telephone operator is not going to call you from there, and if it is supposed to be suspicious. Since you can’t call back, you need to find and use the company’s official customer service phone number. What if I still receive a commercial call from another unauthorized number? You can then file a claim with the Telecommunications User Service Office (OAUT) or a complaint with the CNMC.
What number does each type of call use?. Since introducing prefixes to help identify business calls is nothing new, let’s make a quick summary:
- Prefix 400: Companies call potential customers to offer something.
- Prefixes 800 and 900: These are toll-free customer service prefixes (although they can also be short numbers or geographic numbers), used for ongoing contract management.
Telecos make a move. The 400 numbers are not allocated directly to the company, but to operators: the CNMC opens an initial period of 15 days to request it, on a first-come, first-served basis and assignments in blocks of 1,000 numbers. Of course, since operators are companies that also call to sell, they have already begun to confirm them: Movistar has already informed its customers by email of their new number for discounts and promotions, 400 00 1004, which integrates its well-known 1004, and recommends saving it in the agenda. Digi has confirmed that it will use the numbers 400 120 120, 400 120 122, 400 120 131 and 400 120 134 and it will also mark all commercial calls starting with 400 with a “Commercial Call” notice on the screen.
Also, a service called SoyYo has appeared, joined by companies such as Repsol, Naturgy and Sabadell, so you can check which companies are calling from over 400. What if they try to sell me something from another brand? As the ministry explains, operators will have the obligation to block commercial calls that do not come from 400 based on traffic patterns, such as high volume calls, among other criteria approved by the Secretary of State.
What changes for the company. This obligation to separate your commercial communications from customer service communications affects companies subject to Law 10/2025. In practice, anyone using a virtual switchboard, dialer or communication platform will have an obligation to verify that their provider has already assigned a 400 number and issued sales campaigns from it.
Since numbering is done by operators, companies rely on what their providers have reserved. However, even though the measure went into effect today, the law gives customer service until December 28, 2026 to adapt.
Spain’s anti-fraud scheme. The arrival of 400 prefixes complements the telephone and SMS anti-scam plan that came into effect in May last year. Then there are measures such as the Alias Registry (in force since September 15): a database managed by the CNMC with alphanumeric codes used by companies and public administrations to send SMS, MMS or RCS messages, allowing virtually anyone to check who owns an alias in search engines.
The bad news: The spam will continue. The Spanish government has been trying to eradicate spam calls for years (for example, the General Telecommunications Law of 2022) and today and after many attempts it is still a pending issue. Go ahead and say that this new token will help identify and block those who follow or want to follow the rules, but not identify anyone with intent to scam.
In fact, real number spoofing is still possible as long as there is no end-to-end call authentication. Furthermore, anyone blocked by the traffic pattern will always be one step behind trying to disguise themselves: to make too many calls, they must be made first. On the other hand, Law 10/2025 does not apply to all companies: SMEs are excluded, as long as they do not provide basic services of general interest.
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cover Ivan Linares
