Years ago I got my first internet enabled mobile, and the carrier advertised it as having "300 free minutes" as part of the trial period, which is great. So I used 297 minutes of internet services in the first month, but aha actually the minutes only referred to telephony, and I was stung with a ~12,000 dollar overdue mobile internet invoice (360 dollars per megabyte or something equally ludicrous)

They got done in by a massive class action, that I was tangentially a beneficiary of, not because of the minutes claim, which was standard practice, but because they had failed to provide anyone with the cost of the data.

I think I paid them 300 bucks or something in the end. After further letting a 600 dollar agreement go to collections and settling with collections for 50%.