No mention of data caps? What did you think you were choosing between when you chose a plan?
I would suggest that you post your modem serial number. A rep can pull your sales call and listen to exactly what was discussed.
I don't necessarily agree with your last sentence, but one thing is definitely true...when buying a product, do your own research. Nobody buys a TV without first researching it. The same with a cell phone. People should do the same with an ISP. Unfortunately, so many people seem to forget that.
What I don't agree with is your idea that they are deliberately lying to people because they can. Everyone's entitled to their opinion.