uhm, interesting indeed. Can you pm me with a real extract, even if I don't understand turkish, I think the problem may lie in the character encoding.
what I would do on your side, is to output the content of the string you try to split on your device screen, just to triple check that indeed you are parsing what you expect.
I would also search in general forum for potential issues with turkish encoding and windows phone specifically. I don't see why it work everywhere else but on one device, if that's the case, surely, you are not the only one to have faced this issue. and so I woudl look outside the Unity workd, and certainly in .NET in general.