hey now, Im not tech savvy. My phone is completely dead. how can I restart it in a way that makes sense?

The AT &T store said they did all they could. Also, they said I would need a new phone. The apple consultant who called me said that was unnecessary. I work in a job that requires constant communication. How can expedite this situation so as not to lose work. I do have apple care. I do not have insurance through AT & T.