I have comcast and see some downloads reaching 3MB/s.
Run some speed tests over several days and see what you get. If it is always slow then have them check your lines. Your modem connection should come directly off the first split in the coax line. If you have alot of tvs connected that can cause problems also. You may need to put an amplifier on your line.
Comcast should be able to test your lines and see if there is a weak signal.
You could also complain and see if you can swap out your modem for a new one. I did that and it helped.