is it DSL?
you can get some bad bleed off with DSL if you don't have good phone wire and if you have to many phones. i had to take out my barn phone and replace my phone wiring to get good speed on mine. also, the shorter the line between you box and modem, the better your chances of having better speed.
if your stuff is good, your phone company may have bad lines or be using old equipment. verizon ended up upgrading almost everything out here because they sold DSL to the businesses in town, but were not providing good service.