Did you dial the normal MTN BB10 codes you know and you keep getting the "system error" message each time you dialed the codes? Well, all that simply happened is that MTN changed the codes we know to a new one, unannounced.
here are the latest codes they got replaced with:
Daily Plan (#70): *216*3*1#
Weekly Plan (350): *216*3*2#
Monthly Plan (#1000): *216*3*3#
Enjoy!
Source: http://www.tecnolad.com