iPhone isn't responding, computer won't recognize.

This morning I pulled out my phone, and it wouldn't turn on (I had just charged it for at least half an hour), I got home, plugged it into the wall, and it brought up the apple thing like it does when it dies, so I figured that was all that was wrong, then, a screen came up that told me to connect it to i Tunes, and there was also an info button that brought up the message: "IMEI: Unknown ICCID: Unknown" I plugged it into the computer, and iTunes wouldn't recognize it, and I tried taking out the sim card and putting it back in, and nothing changed, so I don't know what to do. It also says that it is fully charged, and in the top left corner it says "No Service"