it's probably your phone line to blame,
when you signed up you went for a 8Mbs package, if you read the small print carefully it would have been sold as
up to 8Mbs. I take it that you have checked online by putting your number in and it then told you should get about 6Mbs for your area, well those online checkers are never correct!
If you then say your average download speed is about 300kbs then you are actually getting about a 3Mbs connection (Mbs isn't mega
bytes a second, it is mega
bits a second)
you can check your connection speed here
http://www.speedtest.net/
If you are getting 3Mbs (which = about 300Kbs download) then unfortunately nobody will listen to you if you try and complain as you are getting broadband, the fact that it is advertised as
up to 8Mbs and you are only getting 3Mbs does seem a little unfair but that's how it works.
their are a few things you can try to increase the speed, make sure your router is plugged into the master socket for the phone line, buy better ADSL filters as the free ones are normally pretty crap, and also buy a better router (depending on what you already have). getting a netgear router increased my connection by about 1.5Mbs.