While http://www.wayne.hardy.com/ covers a lot of the topic, you have to pester who owns the lines from your house to the next box to get it fixed. There are a few tests you can do. Such as unplugging everything on the line, go find the junction box and giving the terminals a slight tightening, then retesting.
It's also possible your new ISP is at odds with your settings, but you'll have to chat with them about that.
I have 3 Win98 computers, all of which connect to the net via dialup to Verizon, my ISP (Verizon is also my local phone company, and it's their lines we all use). Each computer has a 56K modem, and each has connected at speeds up to 53K at a different location in my county. However, in their present location, each consistently will only connect at 28.8kps.
I once asked a Verizon technician about this and got an explanation (actually only half an explanation) that was hard to swallow: that the underground telephone lines serving my 6-yr old development were limited to 28.8K. If 50-yr old lines in the location where I previously lived and connected could handle 53K, it's hard to believe that newer lines can't. DSL is available in this location, and I believe it uses the same phone lines, but I could be mistaken. Anyway, I don't want DSL; I just want to be able to connect via dialup at a more respectable speed.
If anyone has any ideas or suggestions as to how I can fix this situation, I would be most appreciative. Thanks to all.