It's tricky though, because they have built out, and have to maintain, quite a large infrastructure to cope with voice alone. It extends from billing, through t

It's tricky though, because they have built out, and have to maintain, quite a large infrastructure to cope with voice alone. It extends from billing, through to terminating calls on other networks, running voice mail systems, etc. There's arguably a lot of room for MVNOs only offering data. (In Australia DoDo offered such for the lowest price per GB).