Is my ADSL modem inhibiting my speed?

Title.
I've had AT&T/SBCGlobal as my ISP for a looong time, and the download speed has been pretty stable, but slow.
312 kb/s

What are you paying for? MBPSwise.

I'm not sure, I'll try to find out.
On another note, I did a Glasnost test, and found that it reported my download speed as being what it usually is. It also reported that AT&T wasn't inhibiting my traffic at all. I also checked my modem's page, and saw that the downstream and upstream speeds were what they should be. So I guess it's a service thing
I'll try updating my modem though.

try logging into your default gateway and checking your modem speed. default gateway address is found by

Start>Run>CMD(its also in accessories folder) and typing in ipconfig.

type the ip adress next to "defulat gateway" into a browser of your choice. if the Downstream and upstream on that site does not match up to the service you are paying for, try reseting the modem till it does. If not, its a service problem.

try logging into your default gateway and checking your modem speed. default gateway address is found by

Start>Run>CMD(its also in accessories folder) and typing in ipconfig.

type the ip adress next to "defulat gateway" into a browser of your choice. if the Downstream and upstream on that site does not match up to the service you are paying for, try reseting the modem till it does. If not, its a service problem.

I already know my gateway (and ipconfig doesn't give me the right one anyway), and the Downstream and Upstream roughly match up to my upload and download speeds, with the difference of about 60 KBps. I guess it's just something with the service. It seems all I can do now is talk to my parents about getting a better plan, as they pay about 10 dollars a month for it iirc.