Phone Number Portability: Definition and Impact on a Prospecting File

You switch mobile carriers, keep the same number, and everyone can still reach you as before. It has become so routine that nobody thinks twice about it. Yet this consumer convenience has a direct consequence when working a phone prospecting list: the beginning of a phone number no longer reliably tells you which carrier the line is on, nor even, in some cases, whether it is a mobile or a landline. Here is a concrete definition of phone number portability, the mechanism regulated by ARCEP (France's electronic communications regulator), and what it means when you clean and segment a contact list.

Definition of phone number portability

Phone number portability is the right to keep your number — mobile or landline — when you switch carriers. The number itself does not move; what changes is the carrier that technically manages it. The request goes through your new carrier, who handles everything: you do not need to cancel your old contract yourself.

This right applies to landline numbers, mobile numbers, and value-added service numbers, as specified in ARCEP decision no. 2022-2148 of 6 December 2022. In other words, portability covers the entire national numbering plan, not just mobile numbers starting with 06 or 07.

How portability works in practice: the RIO code and timelines

Everything revolves around a unique identifier: the RIO code (Relevé d'Identité Opérateur — carrier identity reference). You obtain it by calling 3179, a free voice server available every day, 24/7. You pass this code to your new carrier, who triggers the transfer. It is the receiving carrier that drives the process and cancels your old subscription on your behalf.

According to service-public.gouv.fr, the RIO is a 12-character alphanumeric code, and the maximum timeframe to complete a mobile number port is in principle three business days from the date of the request. The obligation to provide a RIO via 3179 has been extended to all numbers by ARCEP, covering both landlines and mobiles. During the switchover, any service interruption remains very brief.

What portability means for the consumer

For subscribers, portability primarily means they can switch without friction. Changing plan, carrier, or package no longer requires notifying every contact of a new number. It also protects a number that has, over the years, become an element of identity nearly as stable as an email address.

Here are the typical use cases it makes possible:

• switching carriers while keeping a longstanding professional number;
• retaining a business landline number when moving offices or changing internet provider;
• consolidating multiple lines with a single carrier without losing numbers clients already know.

Why portability breaks the prefix-equals-carrier assumption in prospecting

This is where portability becomes a prospecting topic in its own right. Before it existed, the beginning of a number faithfully indicated the carrier it had been assigned to. Since a line can now migrate from one network to another, those first digits only reflect the original assignment carrier, never the actual carrier managing the number today. Guessing the carrier from the prefix alone therefore becomes an unreliable approximation.

This disconnect has a very concrete effect on a contact file. A ported number keeps its historical prefix while having moved to a different network, and a single allocation block can now be split across multiple carriers. For routing a call, estimating a cost, or identifying the right network, the prefix alone is no longer enough. This is precisely the problem that HLR lookup (querying the actual current carrier of a number) solves: it queries portability databases to retrieve the current network, not the original one.

Portability and the mobile/landline distinction: what can still be inferred

The good news: portability does not blur everything. The mobile/landline boundary remains largely readable thanks to the French national numbering plan. Consumer mobile numbers still start with 06 and 07, landlines with 01 through 05, and 09 is used for services and platforms. The prefix therefore retains its value for separating mobile from landline, but loses much of its value for identifying the carrier.

In practice, you can still segment a list between mobile and landline numbers using the prefix, and this distinction remains very useful in execution: a mobile is often best reached in the early evening or during flexible slots, while a professional landline connects better during office hours when the switchboard is open. Matching the channel and call slot to the nature of the line is already a way to improve answer rates before even dialling. To explore this logic further, see how French dialling codes can be used to segment a file and why distinguishing mobile from landline changes prospect reachability.

Portability and cleaning a prospecting list: three key habits

Keep the fundamental principle in mind: portability does not invalidate a number, it invalidates an inference. The line is still reachable; what becomes wrong is any carrier information derived solely from the prefix. This leads to three habits to follow in sequence in order to maintain a reliable phone prospecting list.

First, normalise each number to E.164 format (the international standard): this eliminates duplicates and input errors before any further processing. Next, verify the actual assignment via HLR lookup, to confirm whether the line is assigned and active, independently of any portability. Finally, remove dead lines, just as you would apply a dead check to inactive URLs in a contact database. This discipline is precisely what distinguishes a simple export from a true clean, GDPR-ready phone file ready to prospect businesses.

The advantage of an integrated platform like OutSend is that these steps can be run in sequence on an already-scraped list, rather than stitching together a normalisation tool, a verification tool, and a manual re-export. You go from a targeted list of 500 companies built in one hour to a genuinely usable call file, with no gaps between tools.

FAQ — Phone number portability

Does portability apply to landline numbers too?

Yes. The right to keep your number when switching carriers applies to landlines, mobiles, and value-added service numbers, as specified in ARCEP decision no. 2022-2148. A business can therefore keep its company landline number when changing carrier or internet provider.

What is the RIO code and how do you get it?

The RIO (Relevé d'Identité Opérateur) is a unique 12-character alphanumeric identifier tied to your line. You get it by calling 3179, a free service available 24/7, then pass it to your new carrier to initiate the number transfer.

How long does a number port take?

For a mobile number, the maximum timeframe is in principle three business days from the date of the request, according to service-public.gouv.fr. It is the new carrier — known as the receiving carrier — that drives the process and cancels the old contract on your behalf.

Can you reliably guess a carrier from a phone number prefix?

No longer reliably. Portability allows a number to migrate from one network to another while keeping its original prefix. That prefix then reflects the initial assignment carrier, not the actual current carrier. To identify the current network, you use an HLR lookup.

Does a ported number remain mobile or landline?

Yes, the nature of the line does not change with portability. A mobile number starting with 06 or 07 stays mobile; a landline starting with 01 through 05 stays a landline. The French national numbering plan therefore remains readable for separating mobile from landline, even after a port.

Can portability corrupt a prospecting file?

It does not make numbers unreachable, but it invalidates any carrier data inferred solely from the prefix. To keep a file reliable, it is better to normalise to E.164 format, verify the actual assignment of each number, and remove inactive lines, rather than relying on the historical prefix.

To place this topic in the broader picture, browse the complete prospecting glossary.