Unfortunately, while this offer is competitive, it has some caveats. One of the main, regarding included roaming in some countries, is that you should be a customer for more than 60 days. It is written in their conditions (page 3, in Services inclus):
Pass Destination (valables après 60 jours d’ancienneté au Forfait Free): ...
Regarding the prepaid nature of the plan, it is also a bit complex. While you can, through their web interface, usually prepay for international communications, it is not actually a prepaid SIM card (but a postpaid plan) and there is no limit on how much you can spend. Free mobile notifies you when you reach some amount of communications and allows itself to stop your consumption above some threshold. On page 7 of the same document:
Communications au-delà et/ou hors forfait par ligne
Appels/SMS hors forfait sur la période
de facturation de plus de
40€
SMS+ (SMS surtaxés) de plus de
30€
Appels/SMS depuis l’étranger et
Outre-Mer hors forfait sur la période de
facturation de plus de
100€
Internet/MMS depuis l’étranger et
Outre-Mer hors forfait sur la période de
facturation de plus de
40€
And on the following page, the details of what Free mobile can do:
En cas de dépassement du seuil figurant dans les tableaux ci-dessus, l’abonné est informé et invité à payer la somme correspondante depuis son
Espace abonné sur mobile.free.fr. En cas de non paiement et constatation d’un accroissement du dépassement, le service pourra être restreint jusqu’à
la date de la prochaine période de facturation
This also means that to pay, you should go online (you should be able to log in - maybe the information to log in was sent to your hostel).
