I barely get any service on my iphone 5 and I have at

I've had the iphone 5 since it came out and have always had trouble with the service. i barely get ANY service in my apartment, but my roommate, who also has an iphone 5 and at&t, has full service all the time. It is starting to get really frustrating because I don't get people's calls or text messages!

I've contacted apple support but it got disconnected and can't seem to reconnect.

I have toggled with the cellular data turning it on and off, reset my network settings, turned my phone on and off, I do not know what else to do !