Like alot of us my iPhone had the antenna issue. But something was really wrong with mine. My signal would go down and say "No SIM Installed" then my signal would pop up to full bars and then go all the way down to the error again. Here's where it got weird; I would wipe my phone on the back with a microfiber cloth (NOT TOUCHING ANY ANTENNA) and Bam "No SIM installed" INSTANTLY. I even tried a new replacement SIM and still the same thing. I already have it being sent back but maybe the metal SIM tray has something to do with it. If that's the case all Apple has to do is send out plastic sim trays with metal ends to still match the outside of the phone.