What is actually wrong with them doing this? You sign a contract for two years for unlimited data yea. Then after the two years are up they are not contractually obliged to let you keep it. They have so far as a gesture of good will. Obviously they are being greedy but they aren't doing anything wrong, unless they stop you having unlimited mid contract. If that's the case you would be able to cancel as they have not lived up to there end.
Samsung Galaxy NEXUS 4.1.1 Jelly Bean Stock, Stock Kernal (for now)
Samsung Galaxy tab 8.9 3.2 Stock ROM, Rooted
LG Optimus One OFFICIAL CM7.2 @ 806Mhz
LG Optimus Swift ICS BETA ROM