So, a long story short I got a iPhone 3g from my friend, who said that it was working correctly, but somewhat randomly it started saying "the sim card you inserted does not seem to be supported etc.(well you know the stuff) although he had a supported sim card from the original carrier. So he gave it to me and now I'm trying to get it working(so i could use it). I tried restoring it without a sim card inserted so it has the 4.2.1 firmware on it. Can I unlock it without the original carrier sim card and get it working, or is that just impossible?