iPhone won't turn on, and stuck in emergency call

My iphone will not turn on unless connected to its charger is plugged in to a wall power outlet. I can turn it on only when the charger is in, its battery should be charged and when it powers up i tried unplugging it and it only shuts off instantly. But when it turns on it takes me to a screen telling me to connect to itunes, i slide to unlock and it takes me to the emergency call screen. I've tried several different mac computers to try to restore it to a working phone, I've tried connecting during restart, when comp is shut down, or already on, many various ways and with all my efforts nothing works. any help?