Region settings maybe? l once had my nokia n900 refusing to work giving me the sim card error thing. lt was unlocked and a UK version. ln the region settings, it have no Zimbabwe as one of the country it can operate.
l had to change the country settings to SA and chose Econet SA then, put it on dual band and it started working.
So since apple phones work in SA, why not try to set it for SA, it might help and put it to dual!