I got my iPhone 4 yesterday, with a MTN micro sim. I put the sim in the phone and waited 24 hours for the sim to activate. This afternoon when I switched on the phone, it says no service in the left top corner. So I can't do anything with the phone. I phoned MTN, and got transferred and referred all over the place. They say my sim has been active since yesterday, and no one seems to know what the problem is. Any ideas what might be wrong?