This discount card is not issued by NMBS/SNCB Mobility.
You can demand the discount card via your municipality counsil. You receive a form that should be filled out. The form should be sent to:
Service public fédéral Sécurité sociale
DG Personnes handicapées
Centre Administratif Botanique - Finance Tower
Boulevard du Jardin Botanique 50, boîte 150
1000 Brussels
Tel. 02 507 87 99