The Internet Provider (like everyone else said) Has nothing to do with it, but the location of your house from the DSLAM (Digital Subscriber Line Access Multiplexer), this is basically the tele-communication box that your ISP set's you up to, each DSLAM has a 5km coverage area (Converted to miles = 3.1miles) The further away you are from the DSLAM the slower your connection is.
My best tip for reducing lag, found a house closer to the DSLAM