I would need to read the small print (which I probably wont because that would be exhausting and I doubt I would understand it). I'm guessing I have never hit the cap before, then -- becuase I have never been cut off or dialed back in speed that I am aware of.
You are, however, incorrect about isp's "always" having caps. In fact, many of them did not have caps for many years. Proof (and a six month old chart of who DOES and who DOES NOT have data caps here): https://gigaom.com/2013/11/15/data-cap-2013/