Because some areas (and from what I've experienced that includes the majority of PE) there isn't a native 8ta signal. Now normally they let you roam on MTNs network but not with the 10gb accounts.AFAIK it's all 8ta, the SIM works fine in a CellC dongle,and tells you its on 8ta network; have not had any MTN messages/network.....and on the iPad its all 8ta....so why are you thinking MTN?