Unfortunately, 'unlimited' in this case only applies to data being downloaded, but not the speed itself.
However, it is STILL misleading.
A truly 'unlimited service' would not have a speed cap irrespective of the amount of data you download.
It is the responsibility of the ISP to inform the customer about the plan in detail when they are signing up.
True, the guy should have read the fine print, but unless you have a heck of a time on your hands and a lawyer (for those who aren't fully versed in the technicalities of the matter) then you won't be reading it.
If he did ask these questions up front and they deliberately withheld the info, then I suppose he could sue them on those grounds.
On the other hand, they can just as easily claim the fine print says the 'unlimited service' specifically describes a part of their service and not the entire service.
Be as it may, to the 'average joe' it's still misleading.
As for using up 10GB in a month over a phone ...
That's nothing.
A smartphone is a versatile mini computer and not just a phone.
The person in question could have used it for both business and personal aspects (both of which can exceed 10GB very fast).
I regularly go over 60GB per month.
True, I use my laptop for that, but you can easily use the smartphone in the same capacity.
The companies are to blame here really because they still use outdated technologies and charge outrageous prices for the services in question.
It's absurd.