This is a big, and rather complicated discussion. Start here:
http://www.cisco.com/support/toolkit/CableModem/CoS.htm
You would need to get definitions for your COS configured on your port/port group. After that, of course you need to find out your guaranteed minimum downstream rate, etc.
Like I said, this is a pretty big config discussion. I'm doubting you are getting the COS and min data rate of a full T-1 at that price, but for that kind of money, you should make sure.
I run into problems with data link providers even on commercial accounts where they are often run as dynamically adjusted rate using various multiplexing schemes to keep the pipe as full as possible. Sadly, the most common multiplexing schemes are reactive, and cannot predicatively provide data rates for highly bursty, or varied traffic patterns.
There's a lot more to discuss, but the link is a good start based on what I think you're trying to buy.