Sounds like a breach of contract or, at the very least, a false advertising claim.
Boy, was I steaming! Yep, "unlimited" was a false claim. I couldn't believe it when I got my first warning. I wrote to them, but still, after the third warning, they disconnected me. I need to have my Internet running most of the day so I was really thankful when I got Road Runner. Now I can relax and not be treated like a child for being online.