Starting this Saturday, Spain requires identifying commercial calls with the prefix 400: how to block them and complain

Companies that make commercial calls in Spain must, starting this Saturday, do so from nine-digit numbers that begin with the prefix 400. The measure seeks to enable citizens to immediately recognize when communications have commercial purposes and differentiate them, for example, from customer service, according to the Ministry for Digital Transformation.

The new numbering complies with the Law on Customer Service Services (SAC), approved in December of last year, and adds to the measures deployed by the Government against telephone and SMS scams. In this way, operators will be able to block commercial calls made from numbers other than those authorized.

What changes starting this Saturday?

Commercial calls can only be made from nine-digit numbers that begin with 400. That is, when a company calls a potential client to make an offer, the number that appears on the screen must begin with those three digits.

The objective is to make it easier for the user to know in advance what type of call they are receiving and to be able to distinguish an advertising communication from other calls made by a company.

What exactly is considered a sales call?

Commercial calls are considered those made from numbers enabled by companies to contact potential clients and in which a commercial offer is made during the conversation. This differentiates them from customer service calls, which are those that a company makes or receives to manage issues related to contracts that are already in force.

In this sense, customer service departments are outside this obligation. For them, the enabled short numbers, the toll-free 800 and 900 ranges, and geographic numbers may continue to be used. However, the law establishes that a company cannot take advantage of a customer service call to make commercial offers, unless they are related to the resolution of the query, complaint, claim or incident that motivated the contact and, in addition, they represent an improvement for the customer in the conditions of the service or the price.

Who blocks calls and how to complain

Telephone operators will be able to block calls that they detect as commercial and that are made from an unauthorized number. To identify them, they will take into account telephone traffic patterns, such as a high volume of calls, as well as other criteria authorized by the Secretary of State for Telecommunications.

Therefore, the obligation falls on commercial calls: a call from a number that does not begin with 400 will not necessarily be blocked simply because another number is used, but when the operators determine, in accordance with these criteria, that it involves commercial activity.

If a user continues to receive commercial calls from numbers that do not belong to the authorized range, they may file a claim with the Telecommunications User Service Office (OAUT) or report the facts before the National Markets and Competition Commission (CNMC).

Can you return a call to a 400 number?

No. The new 400 numbers will be unidirectional, so they will only be used to make calls: users will be able to receive them, but not dial those numbers back. The Government points out that this feature seeks to increase security and avoid possible fraud derived from returning a call to an unknown number.

What other measures exist?

The creation of the 400 rank is added to the Telephone and SMS Anti-Scam Plan, launched in 2025. According to data from the Ministry for Digital Transformation and Public Service, its measures have so far made it possible to block more than 400 million calls and nearly 32 million fraudulent SMS.

The last measure of the plan before the entry into force of the 400 prefix began to be applied on September 15: an alias registry managed by the CNMC that collects the alphanumeric names used by companies and administrations to send SMS, MMS or RCS messages. Since then, more than six million messages that used an unregistered alias or one registered to another entity have been blocked.

What will the operators do?

Some companies have already begun to explain how they will adapt to the new prefix. Digi has confirmed that from this Saturday it will display the "Commercial call" notice on its clients' mobile screens when they receive calls from numbers starting with 400 and will use this same range for its own commercial actions. Among its most common numbers will be 400 120 120, 400 120 122, 400 120 131 and 400 120 134.

Movistar will use 400 00 1004, a number that maintains its traditional 1004 as a reference. The operator has already begun to communicate it by email to its clients and recommends that they save it in their calendar to recognize their commercial communications. 1004, for its part, will continue to function as a customer service channel.

Avatel, for its part, has announced that it will centralize its commercial calls at 400 887 887, while Orange has already informed its customers that starting this Saturday, commercial communications from the affected companies will be made using numbers belonging to the new range.