Here is how to get 2GB for N200 and 4GB for N400
For 2GB for N200
Dial *482#,a menu will pop up select 1 for 2GB which costs N200.
N/B: The subscription lasts for 14 days.
For 4GB for N500
Select 2 from the menu for 4GB which costs N500
N/B:The Subscription Lasts for 28days.
Both the 2GB & 4GB works on only 2G network.