AT&T Internet Service Slow Internet Speed, Internet

I am paying AT&T for High Speed Pro Internet service and am supposed to be getting 3 Mbps, however, I get less than 1 Mbps. Sometimes, I only get 0.40 Mbps, which is less than one-fourth of the speed I should get.  I constantly check the speed I get by going to the free speed report test at speedtest.net.  I have contacted tech support at AT&T repeatedly regarding this slow Internet speed. Tech support said I was 13,000 ft. away from central line, and maximum distance for 3 Mbps is 10,000 ft. and told me to downgrade to a lesser speed.  Upon contacting AT&T Phone support, the representative says I should be able to get 3 Mbps. I definitely am not getting what I am paying for. I cannot downgrade, because it will become impossible to even get on line. AT&T was recently sued over this problem (people getting far less speed than what they paid for), but unfortunately, I was not aware of the lawsuit in time to be included. When I first upgraded to High Speed Pro, I was getting over 2 Mbps, but over a few month's time it has dropped to almost nothing.