No, it is not considered extortion.  Extortion in the state of Virginia is threatening injury to the person, charachter or property of another (plus a few other elements that have to be proven) and your facts do not seem to fit the bill here. But if they have changed the game plan in the middle I would go and speak with them about working something out with what you have already taken.  See if you were "grandfathered in" as they say.