Clients must be able to set a free block on calls to numbers starting 089, short numbers in format 3BPQ (except 30PQ and 31PQ which are free) and higher-cost numbers as well as SMSs used by firms that bill both for the sending and for service with five-figure numbers starting 3, 4, 5, 6, 7 or 8.
Free Mobile already had a system in place for this. SFR users can sign for its system in shops, via its SFR & Moi app and by customer service.
Orange and Bouygues did not reply to our calls for details.
You can also use a site like nonsurtaxe.com to find a non-surcharged number.