I kinda doubt it's your connection or their end. Not 100% sure, but usually when it comes down to DSL, it depends on how close you are to their DSLAM box. So, it's very possible you're not even capable of getting those speeds on that connection. It can also be the quality of the connection in between the box and your place as well.
When I used to have Verizon DSL, it was capping at 3.0 mbps downstream, although I subscribed for the higher 5.0mbps package. I wasn't able to take advantage of the speed because I was too far from their dslam box. I had the tools to test this myself, so when I did, I called back Verizon and had them downgrade my package for the time being and they didn't have much a problem refunding the difference in charges for the higher tier connection. I've already switched over to TWC 20mbps for now, at least until FIOS is available in my area.
Good luck!