[kbart]

I guess they run as MVNO[1] and all data is routed through their APN. The rest goes as another comment has already described.

1. http://en.wikipedia.org/wiki/Mobile_virtual_network_operator

[ismail]

I seriously doubt this. They would need to sign MVNO agreements with every single operator they support. Unless they have a deal with someone that already has the links to the operators.