Is it the phone or is it your signal? If it's your signal, try disabling 3G when you are home. You may have more bars on Edge and a more consistent signal. The data speeds won't matter if you have WiFi at home. The only drawback is the Edge speaker interference. Regarding the phone shutting itself off, restore it to factory settings. If it continues to shut itself off, tell them you restored it and it continues to shut itself off/spontaneously reboot. Always restore to factory settings before going to an Apple Store for something like this. It may save you a trip.