cant send text messages or imessages and can't log onto imessage

My text messages are very delayed or dont send at all and I can't send Imessages or even log into imessage. All the troubleshooting methods require going to settings then messages but since I can't log in I can't even turn I message off. I've been to my local ATT store and also called Apple support and the problem is still not resolved. Is there anything else I can do? Resetting, backing up and restoring does nothing.