1: Why does a mesivta bachur need a cell phone? Who does he have to call? When?
2: It is EASY to have texting turned off on a plan and very difficult to get turned back on. Same with web access. Just because the phone is enabled with the technology it does not mean that all plans MUST allow the service. By default they do, because the average consumer wnats these features. In the event you dont want them, they can be turned off at the network level and has been stated, is pretty difficult to turn back on. Of course, if your son pays for his own plan and is listed as the owner and he is the one who does all the speaking with customer service, all bets are off.
3: Believe it or not, payphones work just as well. You can carry change or a prepaid calling card foe those occassions a phone call is necessary. I have a hard time believing a yeshiva office would not let a bachur use the phone it there was a legitimate reason for it. If he was in the street, there are payphones around. Unless you are in a horrible neighborhood where these things tend to be vandalized, you should have no such problems. Why would a bachur be in such a neighborhood?