I have an iPhone SE that all of a sudden says "No SIM" when I try to set it up. I used it daily for about a year until I got a 7 Plus. It was taken good care of. I'm trying to set it up for use over WiFi for my younger cousin. I can't set it up without the sim! I've tried many SIM cards, but none work. The phone is still under warranty, but before I send it off, does anybody have any suggestions?