I had the same problem. I left my iPhone 5 uncharged until my lock screen came up but when I put in my password to get in it said no sim card. so I did some research. then I found out that if you eject the sim card on the side with a paper clip then it will come out. after that just take it out and remove the card from the holder then put it back in then put the sim card back into the slot, turn on Wi-Fi, connect and there you have it!