They are just reselling a data pool and clients are connecting via their APN. They are then just applying content filtering via the core network firewalls. This is pretty much what Afrihost and Axxess are doing, except DATA SIM are hoping that their content filter policies will allow them to have users actually use less than R149 worth of data and make a profit on each subscriber. If there are one or two data hogs, the excess data from the majority of lower end data users should subsidize the higher end data users.