I also have the same question. And in general, I think that there are more offers for new users, than for those you are already registered. Such promos are great because sometimes I have no WiFi on campus or at my university, and I need a connection ...
I also had some questions regarding that promo, and I contacted the agent, who helped me pretty quickly. Some users have already provided the link, so I won't do it either, but I can say that support works pretty well.
