The first few years I owned a phone, text messages had not been invented! This was in 1995. I still have the phone stored away and it makes me laught to see just how big it is.
Anyway, phone companies are all rip offs. You will never win. What is particulary sickening in this case is that, they offer you free text massages (implying that they dont cost the phone company anything) yet they charge you a fortune for going over your quota. (when it still costs them nothing). This is very similar to the rip off bank charges we all used to accept.
Steve, if your contract has not much left to run, I would try and bluff them. Ring them up and tell them that you have been offered a new contract with someone else...Its funny just what these cowboys can suddenly do in that situ.