Comcast cut me off last year, after 7 years of service. I got a lil "greedy" and broke the 250g cap (300g+) - never even knew there was a bandwidth meter at their site. By the time they warned me, it was already halfway through the next month. I slowed my usage down, but still broke 260g at the end of the month (I work from home, use it for everything). They shut me off, banned me from service for 1 year, and absolut…
They probably offered you commercial level service during that year (which is more expensive, however has a much higher service level and bandwidth cap)
http://business.comcast.com/smb/services/Internet/plans
If they didn't offer it, I'm pretty sure they'll sell it to you if you want it.