Why is my DSL connection so slow, when my neighbor's is much faster?

"A very helpful AT&T tech that came out to my house ended up solving this issue for me.

The tech measured the signal quality at the point of the phone/DSL wire coming into the outside of my home. The signal quality was just fine at that point (to my surprise)!
The tech measured the signal quality at the phone jack inside my home where I had my router and DSL modem plugged in. The signal quality was very poor at that point.

This proved that the problem was with the wiring inside my home. (Again, this was to my surprise, as I live in a fairly new home that is, in other respects, well-constructed.)

The tech took a look a look at the wiring down in my basement. He offered a diagnosis that the problem was due to the phone wire being run throughout the house bundled together with the electrical power wire. Apparently, per the tech, this can cause interference/""noise"" on the phone line, which can adversely impact the DSL signal quality.

We ended up solving the problem by physically disconnecting, at the junction box in my basement, all of the phone lines running throughout the house except the single line leading to the jack upstairs where I had my DSL modem plugged in. (I didn't care about doing this, as I wasn't using any of the other phone jacks in the house.) This did solve the problem for me, and I now have no issues with my home DSL."

"Switching companies could help if AT&T is in fact limiting or capping your connection speed, the other company hopefully will not.

You did not mention how far from the CO you are, if you are near the maximum distance for DSL from the CO, that could be a factor as well. Your phone line does not alway take the most direct route back to the CO either, you could have a longer cable run compared to your brother-in-law even though he is physically closer to the CO. Depending on your distance from the CO, the line could have gone somewhere else from one of the distribution boxes along the path and that other line may not have been removed, resulting in the line splitting along the path from the CO to your location. That would cause extra noise on the line. If that is the case, switching companies would not help as the local loop would still be provided by AT&T.
Good luck."