Numbers and routing
Number portability
Number portability lets you keep your phone number when changing operator; in France, the request uses the RIO code, obtained by calling 3179.
The new operator handles the process using the operator identity statement the subscriber gives it, and the old contract is cancelled automatically. The right applies to landlines as well as mobiles, with regulated transfer times and limited service interruption.
Why it matters for fax
A fax number is a landline number like any other: it can be ported from one operator to another, including to an online fax service that will route it to a server. Keeping the number printed on years of letters and forms is often what makes a migration lossless.