Have you ever read those things (and actually been able to understand them)? It's ridiculous that it would even be possible for him to run up his bill that high in one month. It would have been one thing if he did it making calls, like if the rate was clearly stated as a certain amount per minute. But he thought he had unlimited internet. You shouldn't need a lawyer to use a cell phone.
You really don't need a lawyer, if you have graduated high school you should be able to read and understand a cellphone term of service fairly easily. I imagine his had something that read similar to this
"NETWORK SERVICES OR NETWORK EQUIPMENT. EXCEPT FOR CONTENT FORMATTED IN ACCORDANCE WITH AT&T¿S WIRELESS CONTENT STANDARDS, UNLIMITED PLANS CANNOT BE USED FOR UPLOADING, DOWNLOADING OR STREAMING OF VIDEO CONTENT (E.G. MOVIES, TV), MUSIC OR GAMES. FURTHERMORE, PLANS (UNLESS SPECIFICALLY DESIGNATED FOR TETHERING USAGE) CANNOT BE USED FOR ANY APPLICATIONS THAT TETHER THE DEVICE (THROUGH USE OF, INCLUDING WITHOUT LIMITATION, CONNECTION KITS, OTHER PHONE/PDA-TO-COMPUTER ACCESSORIES, BLUETOOTH® OR ANY OTHER WIRELESS TECHNOLOGY) TO LAPTOPS, PCS, OR OTHER EQUIPMENT FOR ANY PURPOSE. Service is not intended to provide full-time connections, and the Service may be discontinued after a significant period of inactivity or after sessions of excessive usage. AT&T reserves the right to (i) limit throughput or amount of data transferred, deny Service and/or terminate Service, without notice, to anyone it believes is using the Service in any manner prohibited above or whose usage adversely impacts its wireless network or service levels or hinders access to its wireless network and (ii) protect its wireless network from harm, which may impact legitimate data flows."
The capitals are At&ts own doing, not mine.
That's directly from At&ts terms of service, it's fairly easy to understand and clearly states that the connection: is not to be used for tethering computers and that it is not to be used for downloading, uploading, or viewing content not formated for a phone. They also reserve the right to terminate your data at anytime, which, assuming his cellphone company did the same, they proably should have done (but were not obligated to do). I'm sure there was something similar to this in the terms of service that he agreed to, it's pretty obvious that he didn't read the terms of service. Now if he read the terms and they were not very cleary I would proably feel bad for him, but I would still say that it is his own fault. If there wasn't something like this in his terms, he has every right to have the entire bill reduced to what he would normally pay, but I really doubt a large cellphone company is dumb enough to not make prohibitions on tethering and downloading content. It really is his own fault, this is why you don't sign, or agree to things without reading them.