Signal and data speeds drastically dropped past 2 weeks

We have always had great AT&T signal and data speeds at my home address.  This suddenly changed to pathetic and sometimes nonexistent a few days ago on all devices in my home, neighbors, and others in the area.  I have contacted AT&T 3 times in the past week and a half, had three different trouble tickets and have been told there is no problem.  I have had it.  AT&T refuses to acknowledge something has changed or that there is a problem.  Ready to switch providers immediately and will be doing so.