I guess customers on the Plus tariff simply get bonuses for each recharge and as usual for Lyca all offers are of very limited validity and may be changed at short notice:
http://www.lycamobile.be/en/Free-min...ycamobile-Plus
Fot those interested, here are Lyca's instructions to switch tariffs:
http://www.lycamobile.be/en/Switch-to-Lycamobile-Plus