My friend is in the military and has been in Iraq for almost half a year and he lost his iPhone 4 before leaving. He reported it lost and put his service on military hold, but I found his iPhone after cleaning out his car (kinda just dumped it on me with POA). He said he would be getting iPhone 4s or 5 when he comes back and said I could have it. I took it to an AT&T store and they said the phone can't be used because it's been blocked. I've tried googling this topic and I'm so confused about what I can do with it. If I jailbreak it, can I use it?