Before going on, take a couple of blood pressure reducing pills, and once those kick in, read this paragraph closely:
»
support.cox.net/custsup/ ··· l#aup_13The key sentence is here: "...You must ensure that your activities do not improperly restrict, inhibit, or degrade any other user's use of the Service,
nor represent (in the sole judgment of Cox) an unusually large burden on the network itself...."
I've never seen the numbers for bandwidth use in writing before. Long ago in the days of @Home, I pushed for a definition of heavy bandwidth usage and at that time I was told (verbally by Level 2 tech or above - not sure) that the limit was 500MB data flow total per day
on average ... which works out to about 15GB/month. I was told that people going over the limit once or twice once in a while weren't bothered, that it was only people who continually exhibited "excessive" usage that received such warnings.
Based on what I was told way back then the stated limits of 30GB/7.5GB month seem reasonable (and an improvement from the @Home days). And seeing that some other services have limits as low as 12GB (big to-do about that one about 18 months ago in another forum) the 30GB again doesn't seem out of line.
I would suspect that the most likely culprit that you wouldn't be aware of would be uploads from your filesharing applications -- might get a tool like
DU Meter and see what your traffic flow actually looks like. Without some numbers to toss back at them, you don't have much to fight them with other that bluster and bluff.