One thing with DSL like most other services you have to be careful of is noise on the line!
My DSL service worked great, just over 3.1Mbps and up to 3.3Mbps.....
Here is some information before I go on.
I am on the furthest point on our Loop! they had to install what they call bridges but to you and I would be a range expander, Technically I am about 1/2 - 3/4 of a mile outside the loop, but I have it and it works great.
Recently my service would start to go out on me, just die... then I would get a really slow connection, I called and spoke to someone in Malaysia then someone in India and no one knew what the problem was but they could see a problem, 2 weeks later a DSL Tech comes out to look at my issue.
After being here for 15 minutes he plugged his gizmo into the box on the outside of my house, he said I should be able to get 7Mbps if they would allow it, that's how good the signal is, then we went into my house and he plugged into the outlet feeding my DSL modem... Ohh boy was it bad!
My Modem was running at 100% capacity, they prefer 80% or less, turns out there is a lot of excess wire running around my house acting like an antenna, I took him to the distribution point and he disconnected everything but the one point, does not bother me as I am on a dry loop (No Phone Service).
We went back in, turned the modem off and tested again, now I am showing 40% capacity on my line and can if supplied get 7Mbps, my internet is running so much better and on a daily basis I see a connection of 3.3Mbps down and about 0.8Mbps up, I am happy!
So what you may want to look at is your wiring to start off with, remove anything you don't need to start with or just unplug your service outside of your house and plug direct into it, just to test with.
Other things you may want to check is, make sure you have NO FILTER inline with the modem, you should only have filters inline with your phones, move anything that might create noise (transformers and so on) away from your phone line and modem, do not run phone lines including the one for your modem parallel to power wires, cross at 90° only.
Hope you get it fixed, if not call and have an DSL tech come to your house.
Good luck.